In order to further improve the target positioning accuracy of the semi active laser seeker based on the four quadrant detector,an Infinite integral fitting method(GII)based algorithm is proposed through a Gaussian distributed circular incident spot model.On the basis of the Infinite integral algorithm,taking into account the influence of errors caused by external light energy and dead zones,the least square method has been applied to obtain the analytical expression of the best fit.In order to simplify the calculation of the algorithm,a piecewise polynomial fitting is performed on part of the analytical expressions to optimize the fitting interval,and the analytical expression of the GII algorithm is obtained.Compared with the conventional Infinite integral algorithm and the 8 degree polynomial fitting method,the accuracy of the GII algorithm is significantly improved.Experiments show that the algorithm can increase the effective detection range of the four quadrant detector while ensuring real time performance as well as improve the positioning accuracy of the four quadrant detector under different spot radii,which provides theoretical reference for the development of precision laser guided weapons in the battlefield environment.