In order to meet the requirements of underwater unmanned vehicle（UUV）landing，a hydraulic support rod type bottom auxiliary mechanism is optimized and proposed. A detailed technical design is carried out， and the principle prototype is developed. The test results show that the prototype can withstand water pressure of 2.5 Mpa with support rod expansion rate of 1.8 cm/s. Its roll adjustment ability is bigger than 10° and it has good position keeping ability. Under a ballast of 25 kg，the position change of the support rod is only 0.5 mm after 24 h. The prototype is equipped on an existing UUV for sea trial，and the support function is demonstrated. The research results provide a new idea for underwater bottom-sitting technology.
