The precise extraction of the centroids of laser footprint spots has important practical significance for improving the plane accuracy of laser altimetry by domestic satellites. This paper compared three traditional extraction algorithms of spot centroids, i.e., gray centroid algorithm, Gaussian fitting algorithm, and ellipse fitting algorithm. Then, we proposed a algorithm in which the grayscale and distance thresholds were set by the Gaussian fitting algorithm and Canny edge detection and the spot centroid was extracted by the gray centroid algorithm. The tests of 100 sets of simulated spots reveal that the mean square deviation of the centroid offset extracted by the proposed algorithm is less than 0.05 pixel, and the accuracy is higher than that of the other three algorithms. Furthermore, this algorithm was used to extract the spot centroid of a certain segment of continuous laser data acquired by the Gaofen-7 (GF-7) satellite. The results show that the two laser footprint spots of the GF-7 satellite are within 0.55 cm in the case of ground jitter. Our work can provide a certain reference for the subsequent usage research on laser altimetry data from the GF-7 satellite.