In order to improve the accuracy of the four-quadrant detector used in the laser semi-active guidance system to locate the laser spot center, the positioning principle of the four-quadrant detector is analyzed, and the common positioning algorithms under different spot models are simulated and analyzed. Based on the analysis of the traditional positioning algorithm, aiming at the shortcomings of the positioning algorithm under the Gaussian flare model and combining the characteristics of the standard normal distribution, the positioning algorithm under the Gaussian flare model was reasonably improved. Through simulation analysis and design experimental verification, the results show that the root-mean-square error of the improved Gaussian algorithm is reduced by 60.4% compared with the traditional Gaussian algorithm, which improves the accuracy of positioning the laser spot center position and Linear range.