Passive detection system mainly utilizes signals radiated by the target itself or reflected from external radiationsources for detection. It can perform covert detection tasks without radiating electromagnetic signals, naturally possessing theadvantage of anti-radiation attacks. Its special working system and good detection performance make it the focus and hotspot in thefield of detection technology research. The thesis introduces the main methods and research status of passive detection technologyfirstly, analyzes the key technologies in this field, and prospects the future development trend of passive detection technology finally.