Abstract: In the high speed and heavy load conditions,slipper subjected to external force action will present elastic deformation,and influence the friction and lubrication performance of swash plate / slipper pair,which increases energy consumption and decreases the power transmission effect of axial piston pump. It is necessary to take account of the effect on the power loss of swash plate / slipper pair. To reduce the power loss and improve the energy regulation of axi- al piston pump,a new power loss model was built with the consideration of slipper elastic deformation. The effect of key parameters on the power loss of slipper / swash plate pair were discussed,such as piston chamber pressure,shaft speeds and structure parameters. The results indicate that slipper elastic deformation produces a significant effect on the power loss of swash plate / slipper pair that takes place in the discharge pressure zone of A4VTG90 pump,when the piston chamber pressure and shaft rotational speed are, respectively,set to 21 MPa and 1 500 r / min,leakage power loss is 1. 93-2. 3 W,and viscous friction power loss is 228. 5-240. 3 W. The energy loss of slipper bearing is mainly due to the viscous friction and the leakage power loss is low. Structural parameters,such as the radius ratio of slipper and length diameter ratio of orifice,have a significant influence on the energy loss of swash plate / slipper pair. Appro- priate structural parameters will improve operation characteristics. The range of optimized structural values of slipper: radius ratio of slipper is 1. 2-1. 5,length diameter ratio of orifice is 4-5.