Abstract: The equipment composition, process flow and mechanical structure features and functions of a fullautomatic hydrostatic testing machine with 200 MPa for Φ323 mm steel pipes are described and the key technology of the machine is discussed.Analysis shows that the design difficulties are 200 MPa water pressure boosting inside Φ323 mm pipes, sealing and accurate pressure detection and the key points in design are the ultra-high pressure elements and ultra-high pressure water valve control system.The ultra-high pressure boosting technology, step by step pressure boosting technology and ultra-high pressure water valve control system adopted in the machine can ensure the machine in good operation.