Abstract: The ratio between the outside and inside diameters of the vessel is up to 1. 85, which causes technical difficulties in low sensitivity and defects location when using conventional circumferential ultrasonic detection. In order to solve this problem. A circumferential ultrasonic phased array inspection for the thick-walled cylinder of 140mpa high-pressure hydrogen container was proposed. The ultrasonic field generated by the ultrasonic phased array probe with curved wedges in the cylinder is simulated using CIVA-an ultrasound simulation software. Furthermore, a reference block was designed and manufactured with specific artificial defects, and the relevant experiments were conducted. These results showed that the proposed ultrasonic phased array inspection technology has high detection sensitivity and detection accuracy for the surfaces and the internal defects in the cylinder, and has been successfully applied to the periodic inspection for the thick-walled cylinder in the 140 MPa hydrogen container.