In order to improve the service life of a aviation hydraulic oil tank,its sealing structure was analyzed.The sealing structures of the hydraulic tank which are key or prone to problems were pointed out,and a series of improvements were performed.According to the failure mechanism and the failure reason of the seal,the reliability analysis model of the sealing structure was established through combining and simplifying the failure conditions,and the feasibility of the seal improvement scheme was evaluated.The correctness of the reliability model was verified by the life tests and the practical application of aviation hydraulic tank.The reliability analysis method of the seal parts can be used for the design of the sealing scheme,the design scheme and the fault analysis of the hydraulic oil tank.