Ground coupled heat pump (GCHP) system is regarded as one of the effective energy saving technologies, and obtains popular applications for air conditioning all over the world. However, experimental studies on the GCHP system are still insufficient. In order to investigate the practical performance of GCHP system, the detailed on-site experiments are carried out on a GCHP test rig located in temperate zone. Operation parameters recorded during tests mainly include the temperature distributions of borehole at different depths, the temperature and flow rate of water circulating in the heat pump as well as the ground heat exchanger, the refrigerant pressure, and the power consumption of heat pump as well as circulating pumps. The GCHP system for both cooling provision and heating provision are investigated with two operation modes, which are the intermittent mode and continuous mode. Experimental results indicate that the performance of GCHP system is affected by its operation conditions and modes. Besides, heat and cold accumulation in the ground during cooling and heating provision of the GCHP system are analyzed. (C) 2011 Elsevier Ltd. All rights reserved.