To ensure the safety and reliability of spacecraft during multiple space missions, it is necessary to conduct in-situ nondestructive detection of the spacecraft to judge the damage caused by the hypervelocity impact of micrometeoroids and orbital debris (MMOD). In this paper, we propose an innovative quantitative assessment method based on damage reconstructed image mosaic technology. First, a Gaussian mixture model clustering algorithm is applied to extract images that highlight damage characteristics. Then, a mosaicking scheme based on the ORB feature extraction algorithm and an improved M-estimator SAmple Consensus (MSAC) algorithm with an adaptive threshold selection method is proposed which can create large-scale mosaicked images for damage detection. Eventually, to create the mosaicked images, the damage characteristic regions are segmented and extracted. The location of the damage area is determined and the degree of damage is judged by calculating the centroid position and the perimeter quantitative parameters. The efficiency and applicability of the proposed method are verified by the experimental results.