Acording to the characteristics of the hydraulic circuit of the improved front cover opening and closing device,the T-S fuzzy fault tree is used to analyze its fault. Through the fuzzy possibility of failure probability or failure degree of each component,the fuzzy possibility of fault and the fault degree of the whole device are calculated,which provides a basis for the safety and reliability design of the hydraulic circuit of the improved front cover opening and closing device. The T-S fuzzy fault tree analysis method doesn't need accurate fault probability of bottom events and a large amount of historical data in the analysis process,which has certain advantages over the traditional fault tree analysis method. It can find the weak links of the system and has a certain application prospect in reliability design of equipment.