To find some rules keeping good lubrication condition for plane port pair in high-performance axial piston pump or motor, especially in the very severe applications, a new test rig was built up to simulate the operational principle of port pair, and to form the lubricating oil film for representative parameter acquisition. This rig is principally characterized by supply pressure up to 30 MPa, accurate control of oil film thickness by separate oil circuit design and electrohydraulic feedback control. The tested oil film working properties was analyzed by comparison with theoretical or simulation references. Experiments show that film balance time and thickness are two key parameters for describing oil film properties, and that working condition factors such as supply pressure, lubricating fluid temperature also notably affects the film thickness and its configuration, but they don’t show equivalent action. Lubrication effects can be valued by the tested frictional torque change of port pair.