Abstract: In this paper, a problem is presented that with more fuzzy inference rules based on the same universe of discourse and contained in fuzzy knowledge base, the conclusions obtained by six compositional inference rules respectively will be more derivative from truth. Based on triangular norms, six compositional inference rules are generalized. To solve the above problem efficiently, six compositional inference rules and compositional operators are compared and studied.An important conclusion is obtained’that the selection of the compositional inference rule R’（orR’） and the compositional operator max--T,’ is an optimal one for solving the.above problem.