About multiple applications for graduate programs to the same school Suppose I applied to a Master's Degree Program when I was at my last year in undergraduate. I got accepted but I couldn't enroll at this school because I failed to finish the undergraduate on time, and I need to spend one more semester in undergraduate.

I want to apply again when I'm finished so what I want ask is how my previous application will affect my next one? Will it affect positively since I got accepted last time, will it affect negatively because I rejected the previous one or will it have no affect at all and they will consider my next application independent than previous one?
This is a very good, but very difficult question. The problem is that there's no definitive answer here. 

What we do know:


You turned down a previous offer. This is never helpful for future admissions at a given school.
You were not able to accept because you weren't qualified to start. So long as you clarified this with the school in question, this may be a mitigating factor.


What we don't know:


How the school evaluates candidates. Is it a "rolling" admissions process, in which candidates are considered year round, or is it done on an annual basis?


The last point is probably the most important. If it's a rolling admissions, and you were a high-quality candidate in the previous cycle, you'd probably have a good chance of getting admitted, provided you explain what happened and why you couldn't get in.

On the other hand, if the admissions process is done once a year, then you will have to compete against all of the other candidates in this year's pool. Then, it's not necessarily a given that you would get in having gotten in previously. If you were a "bubble" applicant last time, You may be below the "cutoff" given a different pool of candidates—or you could be a clear admit.