The invention discloses a determining method of the criticality of a fault mode of a rail transit vehicle component. The determining method of the criticality of the fault mode of the rail transit vehicle component comprises the following steps that firstly, estimation scales of risk factors of the fault mode of the rail transit vehicle component are built; secondly, K analysis members are selected for carrying out fuzzy evaluation on the risk factors of the fault mode of the selected vehicle component, a fuzzy decision matrix of the risk factors is obtained, and clear values of the risk factors of the fault mode are obtained according to the gravity center defuzzification method; then a positive ideal solution and a negative ideal solution of the risk factors of the fault mode are determined according to cost indexes of the risk factors, and an optimal solution and a worst solution of the fault mode are obtained; finally, the criticality value of the fault mode is determined according to the optimal solution and the worst solution, and the criticality of the fault mode is determined according to the relation between the criticality value and the optimal solution value and the relation between the criticality value and the worst solution value. The method is combined with the fuzzy theory and the multi-attribute VIKOR decision-making method to determine the criticality of the fault mode, the steps are simple, calculation is small, and the multi-attribute decision-making in the evaluation of the criticality of the fault mode is achieved.