In the analysis of transmission gear fault mode

the occurrence probability of fault

serious degree and maintain ability of failure are considered.And the weight of fault factors is obtained based on experience data and AHP（Analytic Herarchy Process）method.The quantitative analysis of the gear fault criticality is realized through the fuzzy mathematics method.Furthermore

the criticality weight of the failure mode is computed by using Delphi method based on expert inquiry

then the influence of gear fault on higher-up transmission parts is obtained.The results of comparing with Risk Priority Number（RPN）method and criticality matrix diagram method show that

the result of quantitative analysis can be obtained by using fuzzy multilevel comprehensive evaluation

the otherness result can be more acquired on the basis of considering a variety of fault factors

and the support for the fault criticality evaluation is provided.Through the analysis of influence of criticality on higher-up transmission parts

the basis for overall design index distribution is provided.