If you stay in the US for less than 30 days in a calendar year, then you are not liable for any federal income tax for that year.  However, you are still required to pay the federal social security tax contribution (7.5% if employed by a company or business, 15% if self-employed).   Also if you are self-employed, the US Treasury expects quarterly estimated tax payments (subject to a penalty/fine if severely underpaid or not paid at all).  Any income taxes you pay in China (paid by yourself, not by your company) would be considered deductible from your income.

You would also be liable for any state level income taxes.  Luckily for me, I live in an income-tax free state.  Unluckily for me, my sanity requires far more than 30 days a year in the US.

I really recommend consulting with a tax professional.  Helped me out tremendously. 

Actually, from the tax forms I filled out over the years, for federal, if you spend less than 30 days in the US within a tax year, you do not have to pay any tax until you go over a cap of about US$85,000.  Then you will be required to pay taxes (at the 85K+ tax bracket) on any amount over that cap.

There are some ways you can lessen your tax liability by having a housing allowance as part of your pay package.

And as Cooter said, depending on your state of residence, you may be liable for taxes in that state even if you don't live there, own property there, or have anything other than a mailing address in that state.

For example, I was a California resident and I had to pay full taxes on every cent I made in China even though I only had a bank account in the state and nothing else.

Some states do not charge taxes at all, like Nevada (which is why I am now a Nevada resident).

You will need to check with a tax professional depending on how complex your situation is.

One more thing...  If you are legally working in China, you will need to pay Chinese income tax.  Which, depending on how much you make, can go up to around 45%.  And there are no tax returns here, so that money is just gone.  So you may want to see if you can arrange to have your pay amount "after taxes" rather than "before taxes".

You still must file an income tax return regardless of whether you need to pay taxes or not.