my question is, some people get 10 years greencard from the AOS with k-1
that means he dont need to apply anymore, he just stay in country and get his ciztien after 5 years?

If your marriage is less than 2 years old at the time you file for AOS, you will receive a conditional 2 year greencard. 90 days before the 2nd anniversary of the date you were granted conditional permanent resident status, you have to file for removal of conditions.
If you are married for more than 2 years at the time you file for AOS, you will get a 10 year greencard.
If you receive your greencard based on marriage to a U.S. citizen, you can apply for U.S. citizenship 3 years after you were issued your greencard.

You will only get the 10-year GC if you have been married for 2 years or more at the time the AOS is approved.

If you are married less than 2 years at the time the AOS is approved, you will get the 2-year Conditional GC. Then, you must apply to have the conditions removed 90 days before the 2-year GC expires.

You are eligible to apply for Naturalization (citizenship) 3 years after you received Permanent Resident status (GC).

There is language in INA 245 that says that anyone adjusting from K-1 status can only receive conditional LPR status, regardless of the age of the marriage at the time adjustment is approved. There is also contradictory language in other parts of the INA that supports the idea that if the marriage is more than two years old at the time status is granted, the LPR status will not be conditional (that rule definitely applies for anyone who adjusted from some other status besides K-1). People posting here on VJ in the past have reported differing experiences on this point. Apparently different offices read the differing and conflicting provisions of the law differently.

At any rate, it should be a very uncommon circumstance these days for a K-1 visa holder to not finish adjustment of status before the two year anniversary, so the conflicting provisions of the law shouldn't be encountered in practice very often.

Be careful if you're given a ten year card when adjusting from a K-1. Once in awhile they make a clerical error and issue a 10 year green card when they should have issued a 2 year conditional card. Their error doesn't relieve the immigrant of the requirement to apply for removal of conditions if their status should have been conditional.



Either way, if you remain married to and living together in valid marital union with a US Citizen, then you're eligible for naturalization in three years, not five. If the marriage ends (death or divorce) before citizenship is granted, then the requirement is five years.

K-1 or not K-1 (I was never on a K-1) generally when you're married and filing for AOS right when you get married, and this marriage determines your status then yes, in most cases you will get the conditional 2 year GC. Some cases do get held up and those people have to renew their EAD and AP the following year and then maybe after 2 or so years finally get their first GC, in those cases that the AOS took over 2 years to process, they will get the regular 10 year card.

If it's the normal AOS process just from marriage you should only get the 2 year conditional card unless a) AOS takes a long time (over 2 years) or you are getting your green card from employment and during that process you got married and you were nearing the end of that process. Of course they would have already filed their papers and not needed the AOS...