Abstract: In order to achieve imaging, detection and alarm of hemisphere space target by photoelectric imaging system, based on large field imaging and aberration theory, fisheye lens of optical system was theoretically analyzed and simulated by the scaling laws. The barrel distortion and stop coma were used to increase the illumination uniformity of image plane. The system axis aberration decreased by means of ray aiming iteration. Imaging quality of the system was evaluated and analyzed multiply. Distortion correction model of imaging lens was derived. The results show that, in visible spectrum, fisheye lens of excellent imaging quality is gotten, with the CCD effective size of 8.446mm×7.042mm, effective pixels of 2448×2050, entire field of view of 180°, focal length of 2.24mm, relative aperture of 1:2.8, image plane illumination uniformity of over 90%, and mean square root radius value of diffuse spot diagram of less than 1/2 pixel. The modulation transfer function with spatial frequency of 145lp/mm is greater than 0.4. The omnidirectional gaze photoelectric imaging system can realize the real-time detection of hemisphere space target.