Affecting factors for detection accuracy of four-quadrant detector are studied. The effection of facula size, facula centroid position, calculation formula, the noise of detector and amplifier is analyzed in theory, then the effection of these factors is verified by means of calculation and simulation. In the end, a method is proved to be correct by experiment. The research results show that using the appropriate optical system and signal detection circuit, high-precision error detection based on the four-quadrant centroid algorithm is realized.