Abstract: To improve the security of the side power battery pack for electric bus, the breaking protection strategy of the power battery pack was proposed. The side impact finite element model of electric bus BK6122EV was established, then the breaking time of power battery pack and the placement of contact impact sensors were studied. At last, the breaking time at different initial impact velocities and the placement principles of the relevant sensors were concluded. It is significant and valuable for the passive safety of the power battery pack.