Abstract: Based on the upper bond plastic-limit analysis theorem, the assumptions of a Temperature String Model (TSM) of post buckling for multi-tension narrow Steel Plate Shear Wall (SPSW) under fire are summarized, and the upper bound solutions of the allowable shear force of SPSW are deduced. The post buckling bearing properties of narrow SPSW are researched under fire. Also the post buckling for the multi-tension Steel Plate Shear Wall (SPSW) with differing temperature between two ends are summarized, and the upper bound solutions of the allowable shear force of SPSW are deduced. The fire resistance limit analysis of SPSW is studied in the petrochemical furnace equipment, for which the fireproof protection is designed. The application examples indicate that this method is simple and useful, and it can provide a theoretical and practical way for the different fire situation designs of SPSW structures.