This study investigates thermal performance of vertical ground heat exchangers (GHEs) with different inlet water temperatures and borehole depths. The performances of three types of GHEs namely U-tube, double-tube and multi-tube GHEs are evaluated by numerical method using a CFD code. The simulation results show that heat exchange rates per unit borehole depth increase in the cooling mode and decrease in the heating mode of 3.4 W/m for U-tube, 5.7 W/m for double-tube, and 3.3 W/m for multi-tube with increasing of 1 C of the temperature difference between inlet water and ground. In addition, increasing the depth of vertical GHE lowers the heat exchange with the ground. By comparing with 20 m depth, the heat exchange rates per unit borehole depth lower of 32.5 % in 60 m depth, 47.9 % in 100 m depth for U-tube GHE and 29 % in 60 m depth, 42.7 % in 100 m depth for multi-tube GHE, respectively.