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Considering heat and moisture transfer, seepage and freezing simultaneously, a three-dimensional dynamic simulation platform of the ground source heat pump system (GSHPS) is established. Based on this platform, the annual performance of the GSHPS is analyzed. The results show that with the increase of pipe spacing, the soil moisture transfer radius, freezing time and freezing distance become smaller, and the unit performance becomes better. Compared with the pipe spacing of 3.5 m, when the pipe spacing is 4.5 m and 5.5 m, the moisture transfer radius decreases by 11.6% and 20.9% in summer and 6.7% and 15.6% in winter, the freezing time decreases by 25 days and 45 days, the maximum freezing distance decreases by 28.6% and 63.3% in unsaturated soil and 31.7% and 63.4% in saturated soil, and the unit average coefficient of performance (COP) increases by 0.7% and 1.9% in cooling period and 5.2% and 12.1% in heating period, respectively. The moisture transfer radius and freezing distance around the central borehole are the largest, and those around the boundary intersection borehole are the smallest. Compared with all other possible working conditions in heating period, the system performance is the best when considering heat and moisture transfer, seepage and freezing simultaneously. • A numerical model considering heat and moisture transfer, seepage and freezing simultaneously is proposed. • A three-dimensional dynamic simulation platform of the ground source heat pump is established. • Moisture transfer radius of the soil under different pipe spacing is studied. • Freezing distance of the soil under different pipe spacing is compared. • The annual performance of the unit under different pipe spacing is analyzed. [ABSTRACT FROM AUTHOR]