It could be extensive, or not too bad. If you just commute back to China and fly domestic, and the Chinese give you a Chinese tax certificate, you should owe little in the US. If you "work" back and forth to China, the flight time over international waters is taxable income in the US. I have also heard that China Southern doesn't pay tax for your flight time over international waters.

It gets complicated, and the IRS is going after expat pilots in a big way. Over 70% of the expats I know have had the IRS go after them.