I have W2 and try to apply the China-US tax treaty to my tax return with Turbotax Deluxe. Do you know where I should enter the treaty-exempt amount? Thanks!

You seem to be missing the last step of the instructions below.  Remember, you may have to expand the menu to see Less Common Income.  

• In your Federal return, choose the tab for Wages & Income
• Scroll down to Less Common Income (you may have to click Add more income and See more income to view this topic) and Show more
• Start/Revisit Miscellaneous Income and choose Other reportable income 
• Say Yes to continue to the screen Other Taxable Income. Enter your item description and the amount.

Please see the following steps to input your income and your treaty exemption.

1. Click on Federal on the left hand side of your screen
2. Click on Wages & Income
3. Scroll down to Less Common Income
4. Scroll down to Miscellaneous Income , 1099-A, etc
5. Click on Start or Update
6. Scroll all the way down to Other Reportable Income
7. Click on Start 
8. Add a Miscellaneous income item
9. Input description of your wages and wage amount
10. Input your Wages
11. Click Continue and Click Add Another Miscellaneous Income Item
12. Enter your treaty exemption as a negative number.  You cannot exempt more than your total wages.
13. The amounts will offset to zero.   You will be able to see both entries and descriptions on Schedule 1 of your tax return.

You will have to file a Form 8833 to claim an exception. As TurboTax does not support Form 8833, you cannot e-file.  Instead, you may use the program to prepare your return, but need to print out your tax forms and mail the returns along with the form 8833.   Besides the Form 8833 and 1040, you will also need to submit a copy of your tax documents ( for example, W-2 /Form 1099s) which pertain to any credits and deductions you are applying if there are any. 

Form 8833