A method based on weighted least squares surface fitting was studied, which was used for astronomical observation space target. This method can be used in celestial positioning of high-precision and large data quantity, and it is also very simple. Through observing the real sky, the star maps continuously were calculated. The results show that the fitting mean square errors are all less than 4″ in the direction of ascension and declination. The positioning accuracy in the direction of declination is better than that of ascension, the max positioning error of the observed stars are 5.13″and 1.74″ in the direction of ascension and declination . It’s demonstrated that the effects of star centroid errors are reduced, and the match up errors are also removed. The utilization of observed data and the precision of celestial positioning is improved. The method is well suited for application.