Traditional High Power Microwave(HPM) effect assessments mainly use the effect probability curve or failure probability curve to describe the effects of electronics system from the point of view of probability and statistics. However this method is not applicable to the threat level assessment. In this paper，fuzzy decision method is proposed on the basis of analyzing the characteristics and defects of traditional method. Then on the basis of Fuzzy Multiple Attribute Decision Making(FMADM)，a feasible idea is introduced combined by the hierarchical structure of Analytic Hierarchy Process(AHP). The results obtained from examples prove the feasibility of this method. Finally, the problems possible encountering are summarized.