The author established a physical and mathematical model for the heat exchange of a ground source heat pump buried heat exchanger under the co-operation of heat and seepage, including the soil and fluid inside the pipe surrounding the heat exchanger. Using ANSYS finite element APDL language for programming, based on the line heat source model, simulate the temperature field around the vertical double U-tube underground heat exchanger, the effects of soil thermophysical properties, temperature outside the pipe, soil type and backfill material on soil temperature field were obtained through simulation analysis. The experimental results indicate that, the changes in soil temperature are also significant with different backfill materials. Therefore, it is necessary to conduct serious research and optimization on backfill materials, develop new types of backfill materials, improve backfill construction techniques, and conduct in-depth research by combining theoretical analysis with practical engineering to ultimately find efficient and economical backfill materials. The change in equivalent pipe diameter has little effect on soil temperature, and the linear heat source model is used for calculation without causing significant errors. It has been proven that the soil itself has strong resilience and has reference value for the design of buried heat exchangers in practical engineering.