Abstract: Star sensor is one of the key instruments in the celestial inertial navigation system (INS/CNS), and measuring period or update speed is one of the important specifications of it. To satisfy the practical requirements of INS/CNS, the main aspect influencing the data update speed was discussed. A new method was proposed, which made the data acquiring procedure and data processing procedure executed synchronously by arranging subtask reasonably to improve the data update speed of star sensor. The hardware and software of the electronic system which adopted the method were designed properly, and the data update speed of the star sensor was improved from 3.70 Hz to 6.40 Hz, which met the system demand.