The soil temperature change year by year has a bad impact on the operation efficiency of ground source heat pump system (GSHP) which is caused by unreasonable design. Therefore it is necessary to make analysis for utilizable shallow thermal energy stored in the soil in order to realize the good design and application of GSHP system. With a coupled heat conduction and heat advection numerical model for ground heat exchanger, the theoretical calculations are done to make sure the impact of equal thermal energy injection into soil and extraction from soil which is in accordance with utilizable soil thermal energy method, and unequal case. The results show that the soil temperature almost goes back to the original state after one year for the case under utilizable soil thermal energy method. While for the other case with 25％ more thermal energy gain in summer, the mean soil temperature is higher than the initial one by 032 ℃ which is better for the operation in winter time but not for summer time. Therefore, for the cooling load dominated area, the utilizable cool energy amount in summer should be estimated after considering the heat gain of soil in winter and heat loss in intermediate season. It is true for the converse too.