Numerical simulation study on geothermal field of ground water heat pump system is of great significance to the development and utilization of shallow geothermal energy. By building hydro-thermal coupling model of ground water heat pump system by TOUGH2, the change trend of geothermal field and the temperature change of pumping-recharging wells in the study area for years are simulated. The results show that a large amount of cold accumulation appeared in some component parts of ground water heat pump system after 10 years’ operation, which affects heating temperature. Based on the above results and combined with the field site conditions, the solar assisted heat source system is adopted for the system strengthening design aiming at the cold accumulation, the change trend of geothermal field for years in the strengthened system is simulated, and the results show that the solar assisted heat source system can effectively improve the heating temperature.