Laser suffers wavefront distortion in atmospheric transmission. In order to detect the wavefront, we use the Hartmann-Shack (H-S) wavefront sensor to obtain the information of wavefront and locate the centroid of facula by the centroid algorithm. In this way, we can achieve wavefront detection. We put forward the algorithm of rectangular quadrant and obtain the location of centroid by experiment, thereby using the rectangle to enclose the facula. The rectangle can be divided into four parts by axes. The sum of gray values in each part can be determined. According to the geometrical relationship, different formulas are used to determine the centroid for rectangles at different positions. By comparison with the centroid algorithm, it is found that the positions of centroid derived from two algorithms are nearly the same and the speeds of two algorithms are also nearly equal.