It is difficult to obtain critical values of pressure vessel defect cracks accurately. In order to solve this problem, the safety evaluation simulation system for the failure rate and paths of the crack on the aerodynamic pressure vessel was used to find the inflection point of the failure rate in safety critical region and the threshold of aN.The ray method or parallel method did not reflect the real level of dynamic security, but the defects along the failure path which reaches safety critical distance and this distance really reflected the remaining number of cyclic fatigue defects, and a new theory criterion for pressure vessel residual life prediction was established.
