The invention relates to a pressure tank for testing the performance of an underwater connector. The pressure tank comprises a driving assembly, a high-pressure kier, a sealing cover, a test piece mounting assembly and a hoisting component. The driving assembly drives the test piece mounting assembly to vertically move in the high-pressure kier, and the high-pressure kier and the sealing cover arefixedly connected. The driving assembly, the test piece mounting assembly and the hoisting component are mounted on the sealing cover. According to the pressure tank, by testing inserting connectionand separation of the connector under the sealing condition, the pressure environment with the water depth being not larger than 1000 meters can be effectively simulated, and the efficiency of performance detection of the underwater connector is improved; and meanwhile the structure is simple, the performance of the connector can be stably and effectively tested, and the potential application value is achieved.