Low,slow and small targets,represented by UAVs,have revolutionized current militaries,especially in terms of the threat to modern warfare under the complex combat environment.In this paper,through the analysis of various detection means,the absolute advantages of photoelectric detection in low altitude complex background detection is clarified,and the research status of electro optic detecting System is analyzed.Four major challenges faced by the current photoelectric system are introduced:long range detection with large field of view,compatibility between large field of view and high resolution,low false alarm detection and high precision identification of complex backgrounds,and multi target tracking and localization,and the corresponding solution ideas are given as well.At the same time,above four is also the development trend of the electro optic detecting System in the future.Through the improvement of the photoelectric detection capability,the real matching with radar capability can be realized.