The invention provides a bottom support device special for an automobile battery box. The bottom support device comprises a cooling mechanism and a shockproof mechanism, wherein the shockproof mechanism is arranged in the cooling mechanism, the cooling mechanism comprises an outer shell, an installation frame, a dustproof network, cooling fins, comb teeth, a cooling plate and a coiled pipe, and the shockproof mechanism comprises an inner shell, a connection rod, a piston, a shockproof spring and a noise reduction cylinder. Compared with the prior art, the bottom support device has the following beneficial effects that the replacement of the cooling fins is achieved, and the cooling effect is improved; moreover, the cooling efficiency is improved by cycle flowing of cooling water in the coiled pipe, an elastic force is generated by the shockproof spring, the horizontal vibration amplitude is effectively reduced, the shockproof effect is improved, and the stability is high; and meanwhile, the guide function is achieved during the process of the piston horizontally moving along an inner wall of the noise reduction cylinder, the vibration amplitude in other directions is effectively reduced, the shockproof effect is further improved, and the noise reduction function is achieved by design of the piston and the noise reduction cylinder.