Four-quadrant detector is a common position-sensitive device.It is widely applied in the laser collimation,automatic tracking,and other fields.The algorit hm for calculating spot center position is one of the main factors affecting the four-quadrant detector position measurement precision,but it is rarely reporte d.In order to improve the positioning precision of four-quadrant detector,in this p aper we analyze the position error of spot center calculated by current generic centroi d algorithm.Aiming at the deficiency of centroid algorithm,a new high-precision positioning algorithm based on the database query is proposed.The principle of the algorithm is as follows:based on the characteristic of the four-quadrant detec tor and light source,a database is established by simulation.In this database,spot ce nter position and four quadrants′ current ratio of the detector have one to one corr espondence relation.In the practice application,the corresponding spot center location is inquiry in the database on the basis of measuring quadrant′ current ratio of the dete ctor.Simulation analysis and experiment results show that compared with the gene ric centroid algorithm,the new algorithm can improve the calculation precision of s pot center location by two orders of magnitude.It is very important for high pr ecision position measurement by using quadrant detector.