In order to meet the requirements of low energy consumption,long endurance and high control accuracy of AUG,its buoyancy regulation system is generally driven by plunger pump.According to the design requirements,a new micro axial piston pump with combined flow distribution was designed,with a displacement of 0.03 mL/r and a rated working pressure of 25 MPa.The simulation model was established by AMESim software.The simulation results show that the volumetric efficiency of the designed micro axial piston pump for AUG buoyancy regulation system can reach 96% under rated working conditions,and the mass is only 100.2 g,which has a good engineering application prospect.