Can i do my MA thesis on Slaughterhouse_five of Kurt Vonnegut
according to the fantastic Literature theory of Tzveton Todorov? How
the novel can be considered as a fantastic literaature?

You could do this if

1) you could in Vonnegut's interviews places where he has mentioned
Tzveton Todorov and explain what Vonnegut took from Todorov and why he
glommed onto him to begin with.

2) you could identify passages in Slaughterhouse five that are very
similar to passages in Todorov.  Not just in words used, but in
philosophical content.

3) you could find characters in Vonnegut who could just easily BE
Todorov, because of the things they say, because of physical
similarities.

4) you could determine how likely it was Vonnegut would have
encountered the work of Todorov before the writing of Slaughterhouse
Five by researching the number of times Todorov is mentioned in the
index of the Readers's Guide to Periodic Literature, which would be in
bound copies in your library.  Just count how many times he's
mentioned in a given year.

5) Find articles that connect Todorov directly to developments in late
1960s America.  Perhaps as analogy.  Perhaps because Todorov is being
prophetic in the way writers of fiction can be.

6) In your thesis paragraph define what you mean by fantastic literary
theory.  And just go through item by item explaining how Vonnegut's
book falls into this category.

I hope this helps.