In view of the difficult of theoretical modeling of the auxiliary oil film shape and large deviation of the test data,the axial force equilibrium model of the plunger cylinder and the thickness model of the oil film of the plunger cylinder were established,and the fitting algorithm of the oil film shape of the plunger cylinder was further developed based on the circumferential three-point test method of the oil film of the plunger cylinder,taking into account the influence of the force and moment factor,the bias wear factor and the coaxiality error of the main shaft and the plunger cylinder on the oil film shape of the plunger cylinder.The results show that the three-point film thickness fitting curves under the three test conditions are in good agreement with the test curves.The time-varying curves of wedge angle and azimuth angle of the port pair are further solved to lay foundation for the subsequent study of lubrication,friction and wear characteristics of the port pair.