The pressure data of the body surface on CRH6 intercity EMU were recorded through wind tunnel test in a certain percentage. Based on the calculation model of CRH6 intercity EMU, the O-Block structure grid was generated by ANSYS ICEM software. The steady-state data were calculated by using the k-epsilon two-equation turbulence model and the Large Eddy Simulation method was used to calculate the unsteady state data. The error between experimental data and simulation data was within 5%, and met the engineering accuracy requirements. Based on the above simulation algorithm, the three parameters of the transition arc of the roof and the side wall, the transition arc of the side wall and the under frame and the height of the widest vehicle body are the optimization variables, and the smallest overturning moment of the vehicle body is optimization target. At last, the reasonable cross section parameters of the vehicle body are obtained. Research results provide the theoretical basis for the design of CRH6 intercity EMU.