The grounding performance of EMU (Electric Multiple Unit) is related to the safe operation of high-speed train, and unreasonable protective grounding scheme can bring problems such as abnormal wear of grounding brush, high electrical potential of train body, etc. At present, grounding brushes of CRH380B wear seriously and often need to be replaced. Therefore, it is necessary to optimize the grounding scheme of CRH380B. In this paper, a simulation model for grounding current distribution in grounding system of highspeed train is established by pspice software based on the grounding scheme of CRH380B, and this model is validated by comparing the simulation results with that of test in field. In order to reduce protective grounding current and try to improve the evenness of the grounding current. several innovations are introduced to optimizating distribution of protective grounding current based on this model. The findings suggest that the value of grounding resistance and the position of ground points have different impacts on distribution of protective grounding current. Protective grounding current of No.1 car can be suppressed effectively by adding earthing resistance. the change of grounding positions can improve the evenness of protective grounding current distribution. Finally, a mixed grounding scheme is proved to be effective in reducing protective grounding current and improving evenness of protective grounding current distribution. The above conclusions provide a theoretical support for further optimization of protective grounding scheme of CRH380B.