In order to ensure the helicopter for the performance status with overall and holistic evaluation before production，based on the characteristics of the helicopter power supply system， we established the evaluation index system of the power system in design phase, and the pass class hierarchy of that system are analyzed and discussed. Combined with current research situation of the assessment system and the characteristics of the index system, we use the fuzzy comprehensive evaluation method for system property to comprehensively evaluate, especially the establishment of fuzzy assessment model are analyzed in detail. Using analytic hierarchy process(AHP) to determine the index weight of each affecting factor, particularly for the fuzzy judgment matrix determined by different experts we use the least square method(LSM) for more objective and scientific weight distribution. With this method to evaluate the comprehensive property of a certain type of helicopter power supply system, the evaluation result reflects the validity and accuracy of this model.