In fault tree analysis of aircraft hydraulic brake system,the probability statistical information of failure rate for bottom event is usually not sufficient.To solve this problem,a fault tree analysis method based on hyper-ellipsoidal model was given.Firstly,according to hydraulic brake system principle and the failure mechanism,the system fault tree model was established.Then the hyper-ellipsoidal model was introduced to describe the uncertainty of bottom event.Finally,the simulation process of system top event failure probability as well as the importance of bottom events was deduced based on double Monte Carlo method,and comparison was made with fault tree analysis under interval model.Results show that the fault tree analysis method under hyper-ellipsoidal model just needs the value range of bottom event failure probability,without requiring the detailed probability statistical information of bottom event.Compared with the interval model,the hyper-ellipsoidal model exhibits stronger robustness,and its results meet the engineering practice better.At the same time,the importance measurement analysis of bottom events was conducted to identify key failure events,which provides guidance for the brake system in design and maintenance.