Why do I double taxed as self employed person? Form SE impose a self employed tax and form 1040 include self employed Income too and tax it

Sorry yes you pay both regular income tax on the net profit and the self employment tax.  Even if you had no taxable income (like less than your standard deduction) you still owe the SE tax.  If you worked for an employer and got a W2 you would have had the SS & FICA taken out of your paychecks.  This is to pay that part.  It's the same thing.

Self Employment tax (Scheduled SE) is automatically generated if a person has $400 or more of net profit from self-employment.  You pay 15.3% SE tax on 92.35% of your Net Profit greater than $400.  The 15.3% self employed SE Tax is to pay both the employer part and employee part of Social Security and Medicare.  So you get social security credit for it when you retire.  You do get to take off the 50% ER portion of the SE tax as an adjustment on 1040 Schedule 1 line 27 (goes to 1040 line 7).   The SE tax is already included in your tax due or reduced your refund.  It is on the 1040 Schedule 4 line 57 (goes to 1040 line 14).  The SE tax is in addition to your regular income tax on the net profit.