Abstract: In this paper, the radial crack of S31603 / Q345R composite plate pressure vessel was tested by means of ultrasonic straight probe detection, ultrasonic oblique probe detection and TOFD detection (ultrasonic diffraction time difference method) and the defect detection ability was compared. Then, the electron microscopy was used to analyze its failure mechanism. Finally, the safety performance of a pressure vessel with radial crack was analyzed by finite element analysis. The results show that the radial crack was easy to be ignored due to the fact that the ultrasonic plane of ultrasonic straight probe detection was narrow, as TOFD produced a return to the coarse grain of the stainless steel to cover the echo generated when detecting the radial crack. Ultrasonic oblique probe detection was better than direct probe detection and TOFD detection, because the ultrasonic plane was wide. It is recommended to use the ultrasonic oblique probe detection to ensure the safety detection of the radial cracked composite plate pressure vessel. The results of scanning electron microscopy show an explosive composite plate with a clear surface of the sine wave surface and the combination of elements at the surface will be the phenomenon of mutual proliferation. The microscopic defects such as cracks voids and voids in the joint surface can reduce the strength of the bonding surface. Finally, the existence of such cracks put the composite plate pressure vessel at a large security risk by the finite element analysis of radial cracked composite plate pressure vessel.