A series of aerodynamic studies have been conducted to assess and reduce the aerodynamic drag of the HEMU-430X train, the next generation high-speed train with maximum speed of 430km/h including Computational Fluid Dynamics based on 3-dimensional Navier-Stokes equation. Various meshes and numerical methods have been tested to find best way to predict aerodynamic drag of high-speed train. The numerical solutions have been compared with wind tunnel measurements and validated. In addition, Reynolds number effect and moving ground effect have been investigated which can easily be applied to numerical analysis. The contributions of pressure drag and skin friction drag at each cars have been analyzed to assess the composition of aerodynamic drag quantitatively.