Explosion accidents of pressure pipes occurred frequently in recent years. In order to ensure the safety of people's lives and property and effectively prevent pressure pipeline explosion accidents in the process of oil and gas transportation, this paper uses the triangular fuzzy theory to obscure the probability of the basic event of the fault tree, the logical algorithm, and the significance of the basic event in triangle. Via combination of triangle fuzzy mathematics with fault tree, a pressure vessel fault tree chart has been made so as to calculate the distribution range of top-tiered event probability and determine the order of basic event fuzzy importance. According to the calculation, the priorities of the basic events to improve the reliability of the pressure vessel piping system and prevent the explosion accident of the pressure piping are as follows: man-made destruction, aging of the insulation layer of wires near the piping, excessive current in the control room, poor valve seal of the control piping, poor flange seal of the piping and non-standard operation. In light of the fuzzy importance of basic events, the preventive measures of accidents are put forward.