Based on the energy saving demand in operation of a ground water heat pump system (GWHP)，this study analyzes the disadvantages of the original operation strategy and proposes a new operation strategy based on indoor initial temperature. It is validated by a water supply temperature regulation experiment that the new operation strategy can save energy compared to the original operation strategy. The bypass valve closing test is carried out according to the operation status of the system. Both of these tests are carried out in late June. The results show that in similar external weather conditions and trends，the chilled water supply temperature changes from 11 to 12 °C，and the cumulative power of the system in two hours is reduced by 37.8 kW?h. The cumulative power is reduced by 7 kW?h when circulating water pump runs at 35 Hz for three hours after the bypass valve is closed.