The ablation quality under laser micro-scale ablation is an important physical quantity for evaluating performance parameters such as specific impulse in the laser micro-propulsion system. Based on the ablation pit image obtained by the scanning electron microscope, a micro-scale ablation pit shape three-dimensional model reconstruction algorithm was established based on the gray-scale surface reconstruction method; In view of the effect of image noise, the image was segmented and smoothed, which effectively solved the effect of quantization error and grayscale blur on the reconstructed shape, and realizeing the ablation pit volume estimation. The results show that the proposed method can quickly and effectively reconstruct the three-dimensional shape of ablation pits under laser micro-scale ablation, and then calculate the ablation quality.