I am an international student,i want to take SAT,but i have completed my high school last year . will it affect my admission in an reason?
You can still take the SAT after high school. Read this article to get more information about how to do it.
And no, applying to college after you've graduated from high school should not affect your admissions. The only issue that will come up is if you have trouble getting recommendation letters, since recommendation letters are an important part of your college application. There's more detail about how this would work in the answer to your previous question.