If you are marrying someone from China, and plan to sponsor your new husband or wife for a U.S. green card (lawful permanent residence), here is some important legal and practical information.

Immigration Eligibility Based on Engagement or Marriage
First, a little background on U.S. immigration law. Marriage to a U.S. citizen or lawful permanent resident provides foreign-born persons a direct path to U.S. immigration. Contrary to popular rumor, however, they do not immediately or automatically receive green cards or U.S. citizenship.
If you are a U.S. citizen, your new spouse becomes your "immediate relative," and may receive a green card as soon as the two of you make it through the application process. This can take several months.
If you are not yet married and your fiancé is still in China, you can, if you are a U.S. citizen, petition for him or her to enter the U.S. as a fiancé in order to get married in the U.S. -- and then your new spouse can apply for a green card, if desired. You can also choose to get married first in another country, and then apply for an immigrant visa with which to enter the U.S.– the equivalent of a green card.
If you are a lawful permanent resident, your new spouse becomes a "preference relative," in category 2A, and can apply for a green card (and enter the U.S.) only after a visa number has become available. Annual limits on the number of visas given out in category 2A create years-long waits. The application process itself adds more months to the process. Permanent residents cannot petition for fiancés.

Overview of Obtaining a Green Card Based on Marriage
The application process for a green card based on marriage involves multiple steps, such as submitting forms and documents and attending an interview with U.S. immigration authorities. The purpose of all this is to prove:

• the status of the U.S. petitioner (as a citizen or permanent resident)
• that a valid marriage has occurred (or will occur, in the case of a fiancé visa)
• that the marriage is bona fide (not a sham to get a green card), and
• that the immigrant is not inadmissible to the U.S. for medical, criminal, financial, or other reasons.

Procedurally, you may have more than one option as to where and how you apply, as described below.

Procedures When Applying for a K-1 Fiancé Visa
If you and your intended (who lives outside the U.S.) have not yet married -- or have held an informal ceremony that does not count as an official marriage in the location where it was held -- you can apply for a temporary (90-day) visa to enter the U.S. and hold the wedding.
The U.S. citizen starts this process by filing a visa petition on Form I-129F with U.S. Citizenship and Immigration Services (USCIS). After USCIS approves the I-129F, it will transfer the case to the U.S. consulate in Guangzhou, China. There, your fiancé will apply for a K-1 visa, which involves submitting forms and documents and attending an interview.
After your marriage in the U.S., your new spouse can apply to USCIS for a green card, through a process called adjustment of status. The two of you will attend a green card interview at a local USCIS office.

Procedures for Your Spouse to Come From China on an Immigrant Visa
If you and your husband or wife have already married, and your spouse is currently in China, you would start the green-card application process by filing Form I-130 with USCIS. After USCIS approves the I-130, spouses of U.S. citizens can continue forward with visa processing. Spouses of permanent residents will, unfortunately, hit a delay at this point; they'll have to wait (on average two years) for a visa to become available in their category.
Next, your spouse will go through consular processing for an immigrant visa. This means your spouse submits paperwork to, and attends an interview at, a U.S. consulate in Guangzhou, China. (The U.S. petitioner may attend, but is not required to.)
Upon approval, your spouse enters the U.S. on an immigrant visa, at which time he or she becomes a lawful permanent resident.

At Which U.S. Consulate in China the Interview Will Be Held
Although the U.S. has consulates in several cities in China, most of them do not process immigrant visas based on marriage. As of 2012, only the consulate in Guangzhou was handling immigrant visas, which for this purpose includes fiancé visas.
If your spouse happens to be living in another country than China, the consulate there would likely be the one to handle the case.

Procedures If Your Spouse Is Already in the U.S.
If your spouse initially came to the U.S. as a nonimmigrant (such as on a fiancé or student visa or as a tourist), and either you are a U.S. citizen or your spouse is still in valid status, he or she can apply to adjust status in the United States. The main form for this is an I-485. The two of you will attend an interview at one of USCIS’s field offices.
If, however, your spouse entered the U.S. without inspection or by using a fake visa, or you are a permanent resident rather than a citizen, your situation is more complicated than this article can address. You may have difficulty obtaining a green card for your spouse, though it is not impossible. See an immigration attorney for details or if you have any questions about whether you qualify to adjust status.

Entering Into a Legally Valid Marriage
No matter where you marry, you will need to obtain a certificate that convinces the U.S. immigration authorities that it was legally recognized in the state or country where it took place. Below are some tips on doing that.

Obtaining Documentation of a Valid Marriage in China
If you have married, or plan to get married in your fiancé or spouse’s home country, you will first need to look into China’s requirements for legal marriage.
According to information provided by the U.S. consulate, at least one member of the couple must reside in China. Your intended spouse must be at least age 22 if a man or 20 if a woman. And if your intended spouse is still in school, watch out: The school is likely to expel your spouse as soon as you have married, and one school reportedly requires its students to reimburse it for uncharged tuition and other expenses upon withdrawal for the purpose of marriage to a foreigner.
Also make sure that your intended spouse is legally free to marry a foreigner. Certain categories of Chinese citizens, such as diplomats, security officials, and others whose work is considered to be crucial to the state, are not.
Procedurally, you will need to register your marriage with a local Chinese civil affairs office (Ming ZhengJu). You, the U.S. citizen, will need to submit a current passport and a Marriageability Affidavit; the latter can be obtained from the U.S. Consulate, but you may need to have it translated into Chinese by a service authorized by the civil affairs office.The Chinese person must submit a Family Registration Book (Hu Kou Bu) or residence permit, and Chinese National ID card (Shen Fen Zheng).
After the ceremony, you will need to obtain a certificate of that marriage for purposes of U.S. immigration. The U.S. government keeps track of what documents are considered legally valid from each country, and will reject your marriage certificate if it doesn't come from the proper source. What the U.S. is currently looking for is a so-called “notarial marriage certificate” (Jie Hun Gong Zheng or ZhengmingShu)

Obtaining Documentation of a Valid Marriage in the United States
If you will hold your wedding in the U.S., you need to follow the laws of the state where you marry. You will need to obtain a marriage certificate from a local government office. A church certificate, for example, is not enough.