The invention provides a gantry-type automatic spot welding system for a battery pack, which comprises a spot welding device and a spot welding jig fixing device which are vertically arranged and are connected with a PLC (programmable logic controller) of the system. The spot welding device comprises a beam, a group of opposite vertical columns in parallel, a spot welding mechanism, an X-axis sliding table, a Y-axis movement mechanism and an X-axis movement mechanism, wherein the vertical columns are used for adjusting the height of the beam, the X-axis sliding table is used for fixing the spot welding mechanism, the Y-axis movement mechanism enables the spot welding mechanism to transversely move, and the X-axis movement mechanism enables the X-axis sliding table to transversely move. The spot welding jig fixing device comprises a spot welding jig platen and a clamping mechanism for clamping a spot welding jig, wherein the clamping mechanism is arranged on the spot welding jig platen and is perpendicular to the spot welding mechanism. By the aid of a gantry-type structure, clamping is performed once, cells are numerous, spot welding parameters are controllable, and the system is fast in running speed, high in spot welding efficiency, highly adaptable to the cells, accurate in positioning and fine in spot welding quality.