This paper aims at the practical application problems of insufficient lifting force of A frame launch & recovery system for the“Jiaolong”manned submersible. First, a kind of hydraulic system fault tree analysis method is introduced based on the theory of fuzzy. The fault probability of top event and fuzzy importance degrees of bottom events are achieved from experiences and references. In this work we use quantitative probability value, expert experience judgment, and large reliability data to obtain more accurate fault intervals. Finally, the test results show that the fault tree analysis is simple, reliable, stable and easy to use. It can be applied in launch & recovery system for the “Jiaolong” manned submersible.