<p>The alloy in the final stage of solidification is in the semi-solid region, composed of solid grains and liquid film. This article focuses on the effect of liquid film on hot tearing in the final stage of solidification. It investigates the mechanism of the effect of liquid film on the initiation of hot tearing. The mechanical behavior of Al-27%Si hypereutectic Al-Si alloy in high-temperature stress–strain testing was studied. The results showed that the overall content of the liquid film during the solidification process affects the mechanical properties of the alloy; the alloy exhibited viscoelasticity in a high solid fraction state and viscoplasticity in a low solid fraction state. At the same time, a Si-liquid film-Si structure was constructed to simulate the intergranular liquid film structure of hypereutectic Al-Si alloy in the final stage of solidification. The stress variation characteristics of the intergranular liquid film showed that the smaller the liquid film thickness, the stronger the interaction force between Si wafers, which is not conducive to improving the liquid film fluidity. In addition, the fracture morphology of the tensile fracture was observed, and it was found that under the condition of thick liquid film, the flowability of the residual liquid phase was better, making it easier to feed for hot tearing. Finally, CFD simulation technology was used to study the mechanism of the effect of a single factor of liquid film characteristics on hot tearing. The results showed that the thicker the liquid film, the greater its ability to feed and heal the formed hot tearing, thus effectively reducing the alloy's tendency toward hot tearing.</p>