Can I claim any deductions from ordinary business income on Schedule K-1 (Form 1120s) before reporting the income.on my 1040

No, you cannot claim any extra deductions from the ordinary business income reported on your Schedule K-1.

All the allowable expenses must have been claimed by the S-corp which issued the Schedule K-1. The amount reported on Schedule K-1 is your share of the S-corp's net profit after deduction of all expenses.

Thanks!

Incidentally, the S Corp K! is where you will get the new 2019 20% deduction for small business income ala Trump.