A steady RANS approach is adopted to investigate ground effect of high speed trains. Variation of aerodynamic forces due to ground effect is studied. Comparisons of aerodynamic forces on high speed train at different yaw angles and with different ground boundary conditions are performed. It reveals that aerodynamic forces at a yaw angle of 0° are severely affected by the ground effect. As the yaw angle increases, however, influence on aerodynamic forces due to ground effect gets weaker. Influence of height between bottom of the train and the ground is carefully studied. It shows that lift reversal phenomenon exists at different heights and pressure wave on bottom surface of the train takes a linear relation with heights.