A very high accuracy star simulator system with the simulation accuracy less than 0.2″was developed to implement the ground calibration and accuracy testing for an Optical Sensor of Autonomous Navigation (OSAN). The simulator utilizes a high-precision and large size star array target to simulate a star map on the focal plane,and takes a luminescence controllable LED array as the illumination system of the target. Furthermore,it uses a long focal length and large FOV collimator as the projection optical system to control the star map on the target to be alterable and to project from the collimator exit pupil in parallel. Finally, the very high accuracy star map is simulated successfully. A testing method of light projection accuracy is proposed, by which the accuracy level of theory analysis is better than 0.14″. Obtained result indicates that the star simulator can satisfy the requirements of ground calibration and accuracy testing of the OSAN.