The invention relates to an imaging system for a stellar field of computer simulated star sensors. The imaging system comprises an observation star database, a user input end and an extension module. The user input end is created in optical design software ZEMAX and is applicable to setting the direction of an optical axis of an optical module in the optical design software ZEMAX and the quantity and sizes of pixels of an image surface detector. The extension module is applicable to calling the optical design software ZEMAX and comprises an observation star extracting module, a visual field position computing module and a pixel gray scale computing module. The optical design software ZEMAX further comprises a ray tracing module, and the pixel gray scale computing module outputs a digital star chart according to the set quantity and the set sizes of the pixels of the image surface detector and a received energy value. By the imaging system, star chart data matched with the detector can be obtained, image surface data are sampled and quantified by the pixel gray scale computing module according to the sizes and the quantity of the pixels, the sizes and the quantity of the pixels are inputted by a user, the brightness of each pixel is computed, and the digital star chart matched with the detector can be outputted.