如果他能在中国一年待过１１个月好象免交美国联邦税的收入也很多.

Foreign Earned Income Exclusion Form 2555
If you reside outside the United States, you may be able to exclude all or a part of your foreign source earned income by filing Form 2555-EZ/2555 (Foreign Earned Income). You can also get housing exclusion and/or deduction. The foreign earned income exclusion amount for 2007 is $85,700.

To be eligible to file Form 2555, you must meet Bona fide Resident Test or Physical Presence Test. Normally you meet the Bona fide Resident Test if you are a U.S. citizen who is a bona fide resident of a foreign country, or countries for an uninterrupted period that includes an entire tax year. You meet the Physical Presence Test if you are U.S. citizen or resident alien who is physically present in a foreign country, or countries, for at least 330 full days during any period of 12 months in a row. A full day means the 24-hour period that starts at midnight.