The invention provides a personnel leaving detection system. The personnel leaving detection system comprises an ultra wide band main node and at least one ultra wide band auxiliary node which are arranged in a vehicle, wherein each ultra wide band auxiliary node is used for collecting channel impulse response (CIR) information generated by communication with the ultra wide band main node, and sending the CIR information to the ultra wide band main node; the ultra wide band main node is used for detecting whether a vehicle is flamed out and locked or not: if yes, initiating periodic ultra wide band broadcasting to establish communication with all the ultra wide band auxiliary nodes, and after CIR information sent by all the ultra wide band auxiliary nodes in the current broadcasting period is received, operating a personnel leaving detection algorithm to judge whether the personnel are left or not according to all the received CIR information. Due to the fact that the ultra-wideband signals are not easily affected by human body and environment shielding, and the ultra-wideband universal chip has a CIR information analysis function and does not need chip firmware refreshing, hardware cost is low, detection robustness is high, in addition, biological characteristic data collection does not need to be carried out, and user privacy is also protected.