The star sensor has wide application prospect in high precision navigation system of the national defense and people’s livelihood. To acquire ground testing and calibration criterion of the star sensor, the star simulator is more important for the development of star sensor. Therefore, development of star simulator attracts increasingly attention from the scientific research departments all over the world. For the optical structure design of the star simulator, the multi-tube multi-star scheme was finally adopted through fully comparison of various schemes. The implementation of kinds of star function simulation was presented in detail. In the design process, the parameters and indexes of each lightpipe were determined through the theoretical analysis with the Zemax software. Finally, optical parts were calibrated through experimental means and these can meet the user’s demands.