Based on the traditional prediction model of triangular fuzzy accident tree, which had the defect of large error caused by linear approximation, the source of error was analyzed according to the truncated set theorem, and the improved algorithm for drawing membership curve of triangular fuzzy number of accident treetop events was given according to the representation theorem. Matlab software was used to program, the modified and traditional triangle fuzzy accident prediction algorithms were used to predict the electrostatic accumulation accidents in oil depots, and calculated the fuzzy importance of 8 causes. According to the calculation results, compared with the traditional algorithm, the average error value of the fuzzy importance calculation of the eight basic events is reduced by 11.91%，which shows that the modified algorithm greatly optimizes the shortcomings of the traditional algorithm.