Volumetric efficiency is an important technical index for the lifting performance of an oil production single progressive cavity pump(PCP).It is the most used method to obtain the volumetric efficiency by test.In order to improve the design efficiency and reduce the design cost of screw pump,a numerical simulation method of unidirectional fluid-structure interaction was proposed to solve the leakage and calculate the volumetric efficiency.According to the assembly relationship between stator and rotor,the geometric model was established,the stator rubber deformation at the sealing belt under different pressure difference was calculated,and the variation law of deformation with pressure difference was obtained.Taking the field test conditions as the simulation basis,the unidirectional fluid-structure interaction method was used to solve the leakage of PCP under the conditions of test speed and pump pressure,and its volumetric efficiency was further obtained.The simulation results are consistent with the field test results,which verified the effectiveness of using the numerical simulation method of unidirectional fluid-structure interaction to calculate the volumetric efficiency.Through this simulation analysis method,the structural parameters of a PCP can be optimized under the condition of reducing the amount of test,and the operation parameters can be provided.