Abstract: The principle and test method of group bore thermal response tester GP-3 are introduced,and two groups（4 bores in each group）group bore thermal response tests are carried out for the example project. The relative deviations of the thermal physical parameters for individual bore in the group bores is up to 13.71% compared with the average values of these parameters of each bore in the group,while the maximum ones for group bores（as a whole）is only 2.71%. Therefore,the design risk of ground source heat pump system is great when the number of test bores is too small. For large-scale projects with large number of test bores,the test efficiency can be improved with group bore thermal response test,while for small projects,it can greatly improve the reliability of the test results on the basis of slightly increasing the test cost（same test period,greater heating power）.