A fast celestial positioning method based on star identification was proposed to improve positioning accuracy and reduce positioning time. Firstly, the photographic time and angular values were acquired, and the pointing direction of boresight in geocentric inertial coordinate system was calculated by transforming a horizontal coordinate system into a geocentric inertial coordinate system with an astronomical triangle model. Then, all navigation stars and patterns in the area that the boresight pointed were extracted, and the corresponding relationship between stars in images and in the sky was established by a region star match. Finally, the celestial positioning for a space object was completed relatively by reference stars in a background according to pinhole imaging model. The experiment for an image with a FOV of 4°×4°and a resolution of 1 024×1 024 shows that the course of the positioning for the space object has been greatly accelerated due to the introduction of astronomical triangle model and region star match, and the positioning speed is approximately 400 ms. On the other hand, the positing accuracy of a space target is better than 2″ because the relative positioning method eliminates a lot of factors effecting the accuracy.