Abstract: In order to study effect of error signal of a quadrant detector on detection positioning accuracy of a laser seeker, based on the detection and position principles of a quadrant detector, the influence of size of light spot, width of division line and intensity of background light on error signal was studied by means of computer simulation. The results show that bigger size of the light spot will decrease the sensitivity of a quadrant detector and extend the dynamic range. Narrower width of division line is optimal under the condition of good crosstalk performance. The background light will decrease the performance of detector. The study is helpful to improve the detection positioning accuracy of quadrant detectors in laser seekers.