In order to detect concealed body-worn weapon at standoff range, the depolarization effect of radar targets is utilized. By measuring radar echoes of the object at different polarization directions, detection parameters can be obtained and whether the human is carrying concealed weapon or not can be decided. In order to verify the effectiveness of the method, a 140 GHz broadband polarized radar is designed and used to carry out experimental measurements. The experimental results show that, on the one hand, for the firearms, or Improvised Explosive Devices (IED) and other targets that have significant depolarization effect, the system has a better detection effect; on the other hand, the detection of targets with less depolarization effect and the increase of detection distance will result in the increase of the probability of false alarm and probability of leakage alarm and deterioration of the system performance. The system performance can be improved by increasing the size of the transmitting antenna, and the detection performance at the same distance can also be improved by optimizating the detection parameters.