Abstract: In this paper, we use a concept of grey system incidence degree to determine the difference degree between the membership function shapes of two fuzzy subsets and use Hamming distance to determine the close degree between the two membership functions, and thus to determine the optimal solution in the efficient solutions. The step is that the ideal solutions(consisting of the single-object optimal solutions)and efficient solutions(not bad solutions)of multiple-object optimazation questions are made fuzzy to obtain the incidence degree and Hamming distance between separate fuzzy efficient solutions and fuzzy ideal solutions.In the end,optimal solution in the efficient solutions can be determined by ordering and marking.

Key words: Efficient solution, Incidence degree, Hamming distance, Ordering and marking