Aimed to ground source heat pump’s low coefficient of performance in severe cold climate areas, solar assisted GSHP system with seasonal soil heat storage has been advanced. Simulation analysis was done for the underground heat exchanger using finite element method. Changing types of soil and material of U-tube, suitable kind of soil and material of U-tube were found for GSHP system. The analysis result shows that seasonal soil storage can solve the problem of large heat load in heating period and little cold load in cooling period for severe cold areas. It provides theoretical basis for residential use.