The four-quadrant detector is mainly used in high-precision displacement measurement and other related fields. With the emergence of displacement problem in a large number of projects, the displacement measurement accuracy, speed and reliability have become increasingly demanding. In this paper, the measurement principle of four-quadrant detector is analyzed theoretically, the displacement measurement system based on four-quadrant detector is designed, and the experimental platform is built to test and validate the stability, measurement accuracy and range of the displacement measurement system. Experimental results show that: the deviation of the same spot position on measurement system is less than 0.17 mu m. The measurement error of spot displacement is less than 3.7 mu m.