The laser altimeter of the Gaofen-7 satellite is equipped with a laser surveillance camera and a laser footprint camera to obtain laser spots and optical footprint images, so as to assist laser positioning. In this paper, we proposed a method of extracting the footprint spot centroid that took into account the influence of the external environment on the image quality of the footprint spot. The least squares image matching between the footprint spot and the surveillance spot was carried out to obtain the conversion model. Then, the surveillance spot centroid was extracted by the gray centroid method. Finally, the surveillance spot centroid was converted to the footprint spot centroid by the conversion model. The data of 100 groups of simulated spots and 1 track of Gaofen-7 satellite footprint spot were used for the test. The results show that the offset standard deviation of the spot centroid extracted by the proposed method was less than 0.08 pixel and 0.1 pixel larger than those of the gray centroid method and the Gaussian fitting method. 30 tracks of Gaofen-7 satellite footprint spots over a time span of seven months were tested. The results show that both the two footprint spot centroids have a jitter scope of fewer than 1.2 m on the ground, with good long-term stability. The experimental results demonstrate that there is a stable geometrical relationship between the Gaofen-7 laser altimeter laser and the optical footprint image and that the optical footprint image can be used to assist the in-orbit pointing calibration and geometric positioning processing.