In order to improve the simulation speed of space-based large-field optical observation star map, a fast simulation method for space-based large-field optical observation star map is proposed. First, the imaging principle of real star map is explained, and the simulation process of space-based optical observation star map is designed. Then, by analyzing the calculation methods of each process, it is concluded that the calculation of the point spread function is the main factor affecting the simulation speed. Finally, combining the imaging mechanism of the CCD device and the characteristics of the real image, an adaptive point spread function is established to realize the rapid simulation of the space-based large-field optical observation star map. The simulation experiment shows that this method can increase the simulation speed by about 47% compared with the traditional imaging method while ensuring the fidelity of the imaging, which plays an important role in the development of the space-based optical observation platform.