The accuracy of the four-quadrant detector on the target directly affects the guidance precision of the laser guided weapon. Therefore, it is very important to study the accuracy of the four-quadrant detector. In this paper, the method of computation and simulation analysis was adopted, based on the uniform distribution of the pulse peak power density at the entrance of the seeker, and the noise interference current obeyed the Gaussian distribution, and the beam deflection angle error model of the laser seeker was established; however, the beam deflection angle error had random probability due to noise interference, so the mean and standard deviation of the beam deflection angle error were used as the measurement of the four-quadrant detector angle measurement accuracy. The relationship was established between the mean and standard deviation of the beam deflection angle error and the optical parameters of the seeker, the spot radius, the incident angle of the diffuse reflection laser, the noise interference current, and the pulse peak power density at the entrance of the seeker. Taking the standard deviation of the deflection angle of the seeker beam as an example, the simulation analysis was carried out in combination with the application background.