the present invention discloses a back - scatter human body security inspection system , capable of detecting a radioactive matter carried by the human body , comprising : a radiation source configured to generate radiation rays , a flying spot forming device , configured to modulate the radiation rays from the radiation source , so as to form flying spot scanning beams for scanning the human body to be detected , a detector configured to detect radiation rays from the human body to be detected and output a signal characterizing a dose of the radiation rays , a control and data processing device , configured to process the signal outputted from the detector to obtain a radiation image of the human body to be detected . the detector detects the radiation rays from the radiation source scattered by the human body to be detected , separately at different times , and the radiation rays from the radioactive matter carried by the human body to be detected . in the present invention , the application ranges of the back - scatter human body scanning apparatus can be effectively expanded , without adding and modifying the hardware therein , thereby increasing the monitoring function to the radioactive matter carried by the human body and further improving the effects of the human body security inspection .