Ground　source　heat　pump　has　the　advantages　of　high　efficiency,　energy　saving　and　environmental　protection,　which　fully　develop　and　utilize　the　shallow　ground　heat　energy　and　other　renewable　energy.　For　the　better　using　of　ground　source　heat　pump,　there　are　still　many　issues　need　to　study.　Because　of　the　low　evaporation　temperature　of　ground　source　heat　pump　system,　the　quantity　of　refrigerant　charge　has　a　greater　effect　on　the　COP　of　heat　pump.　In　this　study,　an　experimental　setup　of　ground　source　heat　pump　system　is　established,　and　the　effects　of　different　refrigerant　charge　on　the　operation　performance　of　the　heat　pump　unit　are　investigated　by　varying　the　refrigerant　charge　quantity　of　R22.　Through　analyzing　the　experimental　results　and　reasons　in　thermodynamics　theories,　the　influence　degree　of　refrigerant　charge　quantity　on　the　performance　of　ground　source　heat　pump　system　and　the　optimal　refrigerant　charge　quantity　for　the　existing　heat　pump　are　obtained.　The　experimental　results　can　provide　theoretical　and　application　bases　for　the　ground　source　heat　pump　system　efficiently　running　and　the　sufficient　use　of　energy.　Copyright　©　2009　by　ASME.