Generally, it is said that the ground source heat pump (GSHP) can operate with less power consumption than the air heat pump. With a direct expansion method GSHP, it is possible to terminate the evaporation/condensation process of the refrigerant within the geothermal heat exchanger within a depth of 30 m by a proper design, but we need think about the heat collection and release characteristics during high load continuous operation. Therefore, the behavior of water in the bore hole that insert the heat exchanger was obtained by three-dimensional numerical analysis, and the heat collection characteristics in the bore hole during heating and hot water supply operation were investigated.