The invention discloses a battery pack with a bottom fixed plastic battery shell. The battery pack comprises batteries, a fixed box body and a baffle plate, wherein the each battery comprises a battery shell, the battery shell is in a square shape, a bottom fixed structure is arranged at the bottom of the battery shell, bottom fixed holes and bottom bolts are arranged at the bottom of the fixed box body, the batteries are fixedly connected with the bottom fixed holes by the bottom fixed structures of the battery shells, the baffle plate is provided with a side wall, an upper folding wing and a lower folding wing, the upper folding wing and the lower folding wing are bent along the side wall, support fixing holes are formed in two ends of the upper folding wing, bolt fixing holes are formed in the lower folding wing, and the bottom bolts are arranged in the bolt fixing holes in a penetrating way. By the battery pack with the bottom fixed plastic battery shell, the batteries can be rapidly assembled, are fixed with the fixed box body and are reinforced by the baffle plates, the process is simplified, the labor intensity is reduced, a fixed part is reduced, the weight of the batteries grouped is reduced, the specific energy of a battery module is improved, and meanwhile, the reliability after grouping the batteries is improved.