The invention provides a spot welding jig for a polymer battery core. The spot welding jig comprises a carrier base structure, a carrier part, an elastic device and a pressing structure, wherein the carrier part is mounted at the upper end of the carrier base structure; the elastic device is arranged on one side of the carrier part; the pressing structure is arranged on the other side of the carrier part; the elastic device is matched with the pressing structure; the elastic device comprises attaching parts, protecting parts, elastic parts and a connecting part; the plurality of protecting parts are connected at the upper end of the connecting part through the elastic parts; the attaching parts are arranged on the protecting parts; the protecting parts are connected with the carrier part; the pressing structure comprises a shielding part, a B profiling part and locating pins; the shielding part is fixed to the B profiling part; and the shielding part is clamped on the carrier part through the locating pins. According to the spot welding jig, elastic attaching is achieved, molding and secondary molding of special shapes are achieved, the defective rate is decreased, the operation procedure is reduced, the production efficiency is improved, the production cost is reduced, the processing quality of products is guaranteed, and requirements of customers are met.