In order to better analyze floating production storage offloading （FPSO） faults and construct an FPSO fault evaluation system， this paper uses analytic hierarchy to conduct fault attribution research on FPSO. The three elements of three-phase separator， electrodehydrator and sea pipe of FPSO oil， gas and water separation system were selected as the research objects， and the structural model of hierarchical analysis was established by processing and analyzing the causes of system failures. The hierarchy is used to judge the failure factor indicators， and the weight value of each failure factor indicator is calculated to analyze the cause of the failure. The results show that the weight of electrodehydrator faults is large and the degree of influence is also large， and the weight values of each index level can be well compared through hierarchical analysis to judge the degree of influence in each level.