Three types of alumina surface irradiated by laser are simulated in this study to investigate stray light ablation. Results indicate that temperature fields of triangular and rectangular microstructures exhibit the "head effect," while overall still exhibit Gaussian distributions. For the stress, there is a notable difference between the microstructure surface and the ideal surface. The most stress concentration occurs at the corners on the microstructure surface termed as the "bottom effect." The maximum tensile stress of a triangular microstructure appears below the midline of the slope. The location of the maximum tensile stress on the triangle first shifts down and then up. The inflection point is 0.9 µm in height of the triangle.