This paper deals with the new important properties about the fuzzy set boundary in fuzzy topological spaces, If (?)={A_α;α∈Λ} is a locally finite family of fuzzy subsets of a fuzzy topological space (X,τ). we shall prove the following: (1) The family of boundary of members of (?) is also locally finite, (2) The union of boundary of members of (?) is closed, (3) The union of boundary of members of (?) contains the boundary of the union of members of (?), (4) b(E×F)(?)(b(E)×(?))∪b(?)×b(F).