To satisfy rigid performance specifications, a feedback control was presented for zoom optical lens plants. In order to improve the angle measurement accuracy of the star sensor, a novel approach is proposed as the model updating and angle measurement accuracy testing of the star sensor using system identification. First, the theoretical measuring model of the star sensor and the spatial relation between image coordinates of the star sensor and target are analyzed. Secondly the basic principle and the measurement model are given for getting more accurate measuring model by updating the model of the star sensor. The correction model of the star sensor is established by means of system identification technique. For improving the angle measurement accuracy of star sensor，the CCD image plane of star sensor is divided into multiple regions, and the model of every region is built by system identification individually. The experiment is conducted with a star sensor. The experimental results show that the angle measurement accuracy of x and y directions is 1.68″ and 1.91″ after calibration, but 17.43″ and 23.46″ before calibration. The results show that the angle measurement accuracy of the star sensor is improved with this method.