Volume loss power and mechanical loss power of the aviation piston pump and the physical characteristics of oil under the influence of variable temperature and pressure were analyzed in detail. The efficiency model of the piston pump was set up considering the effects of oil temperature, load pressure, input rotational speed and swash plate angel. The hydraulic system with the piston pump as a part was simulated, and the three-dimensional cambers of the piston pump efficiency under different conditions were obtained. The research provides reference for the design and application of piston pump.