Abstract: External corners of concrete floor slabs are prone to non-structural cracks under temperature loads, which adversely affect residential comfort and durability. To address this issue, this study aims to quantitatively elucidate the influence of temperature on the mechanical response and cracking behavior of slab corners. Taking a real residential concrete floor slab as the research object, field inspections were first conducted to obtain crack distribution characteristics and material parameters. Subsequently, incorporating actual boundary constraints, a three-dimensional solid model was established using ABAQUS finite element software. Numerical simulations were performed to analyze the tensile stress distribution and crack evolution in the corner region under a temperature drop of 30 °C (from 50 °C to 20 °C). The comparison results between on-site testing and numerical simulation show that under a temperature difference load of 30 °C, the peak tensile stress of the external corner calculated by finite element method reaches 1.89 MPa, which is the ultimate tensile strength of the relevant concrete, indicating the risk of cracking in this area; The simulated crack zones are mainly concentrated within a range of 0.3 m to 1.0 m from the corner of the shear wall, forming an angle of about 45° with the wall. The simulation results are highly consistent with the measured crack morphology and distribution intervals. In summary, temperature-induced stress concentration is the core factor inducing corner cracking in floor slabs. The finite element model established in this study accurately reflects the mechanical response of the corner area, providing a reliable quantitative basis for optimizing corner reinforcement schemes and formulating temperature crack prevention measures in similar engineering projects.