Sapphire is often chosen as the observation window in shock wave experiments due to its excellent strength, hardness and optical transparency. A deep understanding of the mechanical and thermodynamic response mechanisms of sapphire under impact loading and the causes of internal damage is crucial for accurately evaluating its performance and stability. In this work, molecular dynamics simulations were performed to explore the mechanical and thermal response of a sapphire single crystal under shock loading along the C-plane. The results indicate that the activated slip system after the impact loading is the rhombic plane slip based on the R-plane { $0\overline{1}12$}. When the impact velocity is in the range of 1−3 km/s, no slip occurs; when the impact velocity reaches 4 km/s, slip occurs. When the impact velocity reaches to the range of 5−6 km/s, the sample shows inhomogeneous deformation, mainly composed of irregular stripes. Such results suggest that the activation of the slip system in sapphire depends not only on its lattice structure, but also on the partial shear stress (which needs to reach a critical value). The analysis of the temperature field indicates that there is an intrinsic relation between the local slip and temperature increase, i.e., the formation of intense shear localization is accompanied by the higher temperature.