In consideration of stray light sources of a star photoelectric-detection system, this paper analyzes the generation of the stray light and its transmission characteristics, and proposes how to evaluate the effects of stray light on the photoelectric-detection system. A reasonable suppression scheme for the stray light is provided for guiding the design of opto-mechanical structure of the system. Then the main baffle, baffle vane and the coating technology are used to eliminate the effect of stray light on the opto-mechanical structure. The opto-mechanical structure of the system is simulated by a software and the results show that their Point Source Transmittances (PSTs) before and after eliminating the stray light have been reduced by two orders of magnitude between 10-8 and 10-10. Meanwhile, the obtained detection data in experimental field demonstrate that the scheme can extract a detection im-age with 5 star magnitudes, and the stray light has been suppressed effectively.