Abstract: The pump efficiency of some deep pump wells is poor in Zhongyuan Oilfield.To solve the problem,research on hydraulic compensating pump has been carried out,which is aimed at increasing pump volumetric efficiency.By analyzing the affecting factors of pump efficiency,the hydraulic compensating pump and anchoring elements have been developed including conceptual design,lab experiments and field tests.This compensating pump system consists mainly of oil well pump,hydraulic compensating pump and anchoring element.The mechanism of this pumping system is as follows: the energy created by tubing extension and shrinkage during upstroke and down stroke will be applied to increase the instantaneous pressure in hydraulic compensating pump barrel,so that standing valve of oil pump is forced to open and pump volumetric efficiency and pump efficiency will be increased.Field test results show that hydraulic compensating pump can work synchronously with oil well pump without special operation while oil production process.Application of this new mechanical oil recovery system can improve pump volumetric efficiency and increase pumping efficiency.