<p>Post-earthquake fires and aftershocks cause significant damage and are the most common and significant secondary disasters. This study conducted a simulation to assess the effects of fires and aftershocks and established a 5-piece T-shaped short-limb shear wall model using the finite element software ABAQUS and the ISO-834 standard fire curve. The evolution of the temperature field and seismic performance of the short-limb shear wall exposed to high temperatures of a three-sided fire was evaluated. The results showed that the temperature field exhibited a left–right symmetric ripple distribution, and the wall temperature decreased from the fire-affected side to the other side. The seismic performance of the specimens decreased with increasing temperature, and the damage pattern was a through-crack extending from the base of the wall limb and the middle and lower part of the web to the centre of the web. Specimen SWT650-3 exhibited optimal seismic performance when exposed to high temperatures, with a limb thickness ratio of 6.5, an axial compression ratio of 0.2, and a stirrup ratio of 1.82%. Models were used to investigate the impact of the axial pressure ratio, heating time, limb thickness ratio, and protective layer thickness on the seismic performance of the T-shaped short-limb shear walls. The higher the axial pressure ratio within a specific range, the more significant the damage to the specimen. The heating time substantially influenced the specimen’s load-bearing capacity at high temperatures. An appropriate increase in the length of the wall limb improved the load-bearing capacity of the short-limb shear wall, and an increase in the thickness of the protective layer improved the fire resistance.</p>