Abstract: In order to improve the operation efficiency of ground source heat pump, this article carried out performance tests on actual ground source heat pump system under different refrigerant charge quantity of R22 from external water circle side and inner refrigerant side simultaneously. This article analyzed the performance states of ground source heat pump and the reasons from thermodynamics and system theory, and determined the degree of influence of refrigerant charge quantity on the performance of ground source heat pump system, finally provided the optimal refrigerant charge quantity.