A three-dimensional finite element dynamic simulation platform of the ground source heat pump system (GSHPS) is established. According to the outlet temperature of ground heat exchangers (GHEs) required by the code in summer and winter, the calculated minimum buried depth of GHEs meeting the requirements is 60 m, when the number of borehole is 9. By using the established platform, the annual operation performance and cost of the GSHPS under different buried pipe depths are studied. The results show that the deeper the buried depth of GHEs is, the better the heat exchange effect of GHEs is. Compared with the GHEs with 60 m buried depth, when the buried depth of GHEs is 65 m, 70 m, 75 m and 80 m, the average coefficient of performance (COP) of the unit increases by 4.1%, 6.3%, 7.7% and 8.2% in cooling period and 1.0%, 1.6%, 1.8% and 1.9% in heating period, respectively. Considering the performance and initial investment of the GHSPS comprehensively, the optimal buried depth of GHEs is 60 m. However, considering the performance the system and the total cost of the system running for 20 years comprehensively, the optimal buried depth of GHEs is 70 m.