I have a son, he is working a part time and the same time he studies, I help him, how can I file tax return

Some questions which you need to answer for us to understand your situation better:

1. How old is your son?
2. If he is under 24, does he provide less than half of his own support, and does he live with you at least half-time? If he is between 19 and 24, is he a full-time student?
3. If he is 24 or over, do you provide at least half his support, and is his income less than $3400?

This will allow us to tell you whether you can claim your son as a dependent.

My son is 19 I provide support, he lives with me, he is a part time student

My son is 19 I provide support, he lives with me, he is a part time student

By IRS rules he is not a quaifying child (if age 19-24 he must be a full time student to be a quaifying child), but he is a qualifying relative for you if his gross income for the year is less than $3,400 and if you provide at least half his support. Does he meet those two conditions?

Yes, your son does not qualify as Qualifying child unless he is full time student for at least 5 months in a year.
He can be Qualifying Relative if you meet the requirements. Read:
Your U.S. Tax Return: Requirements for claiming a dependent (http://taxipay.blogspot.com/2008/03/requirements-for-claiming-dependent.html)