I would like to claim dual status tax return in 2019. Do I need to file 1040NR if my US source income is 0 as a nonresident alien? Or just form8843?

You need to file Form 1040-NR.  You can download a copy from IRS.gov, complete and mail in, or you can go use SprinTax:

TurboTax doesn't support Form 1040NR: U.S. Nonresident Alien Income Tax Return, but we have a partnership with Sprintax offering a nonresident tax filing solution to our TurboTax customers.

Visit the TurboTax/Sprintax site for more info or to get started.

Thanks David, as you said I needed to file both 1040 and 1040NR, and 1040 should be a statement as I become a nonresident alien at the end of 2019. Just wonder whether I should copy all the income from 1040 (from W2 when I was a resident alien) to 1040NR to claim the tax return? Or just keep all lines to be $0.

If you do not have any US source income on Form 1040-NR, enter all zeros. 

@zhanglu295