Pressure and performance requirements of axial piston pumps and the proportion of churning losses in axial piston pumps increase significantly with increasing speed. To investigate the primary distribution of churning losses in axial piston pumps at various ranges of speed, a test rig was set up in which other friction losses can be eliminated, thus making it possible to investigate the net churning losses in an axial piston pump. The influence of the rotating cylinder block and pistons on churning losses is analyzed based on a qualitative evaluation of the various fluid flow regimes at different test speeds in an axial piston pump. The analytical results indicate that pistons have less influence on churning losses than the rotating cylinder block beyond the critical speed in axial piston pumps, because the total energy dissipation transforms laminar viscous friction losses into turbulent shear stress losses. It is concluded that more attention should be given to the effect of the rotating cylinder block on churning losses in axial piston pumps at high rotation speed.