An automatic spot location and extraction algorithm based on the combination of the Otsu method and the centroid method is proposed herein for the grating wavefront curvature sensor and verified through experiments. The original intensity distribution image is first binarized by using Otsu method. Then, the binary image is then segmented into two binary images according to the centroid coordinates such that each binary image contains one spot. Finally, the centroid coordinates of the two images are calculated as two spot centers in the original intensity image, while the two spots in the original image are extracted from the original intensity image. An experimental setup of the grating wavefront curvature sensor is built based on an off-axis Fresnel zone plate to verify the effectiveness of the proposed algorithm. In the experiment, the spots are extracted automatically by using the above algorithm; then, the wavefront is restored by using Laplacian eigenfunctions. The results are compared with those of the Hartmann wavefront sensor. The experimental results demonstrate that the proposed algorithm can extract spots automatically with an error less than 4 pixel.