The invention provides a spot welding system for electrode plates of a power battery pack, which comprises a spot welding device and a spot welding jig clamping device which are oppositely arranged side by side and connected with a PLC (programmable logic controller). The spot welding device comprises a bottom plate, a lateral plate, a lifting table, a spot welding mechanism, an X-axis movement mechanism and a Z-axis movement mechanism, wherein the X-axis movement mechanism drives the lifting table to longitudinally move, and the Z-axis movement mechanism drives the spot welding mechanism to transversely move. The spot welding jig clamping device comprises a spot welding jig sliding table, a clamping mechanism and a Y-axis movement mechanism, wherein the clamping mechanism is used for clamping a spot welding jig, the Y-axis movement mechanism drives the spot welding jig sliding table to transversely move, the clamping mechanism is arranged on the spot welding jig sliding table and is perpendicular to the spot welding mechanism, and the Y-axis movement mechanism is connected with the spot welding jig sliding table. Besides, two sliding rails beneficial to sliding of the spot welding jig sliding table are arranged below the spot welding jig sliding table. The spot welding system is an intelligent full-automatic spot welding system, which is high in efficiency, low in consumption and high in welding quality.