The invention discloses a protective radar safety detection semi-trailer which comprises a trailer head, a trailer plate, anti-collision safety components, a protective component, damping and buffering components. A controller is arranged in the head, the rear end of the head is connected with the front side of the trailer plate, the protective component is arranged on the rear side of the head, the protective component is used for preventing the rear side of the head form being collided, the anti-collision safety components are arranged on the left side, the right side and the rear side of the trailer plate and used for preventing the lower side of the trailer plate from being involved, the damping and buffering components are connected on the anti-collision safety components, the dampingand buffering components are used for damping and buffering when the trailer plate is collided, first radars electrically connected with the controller are arranged on the front side of the head andthe left side and the right side of the trailer plate, and a second radar electrically connected with the controller is arranged on the right side of the trailer plate. According to the semi-trailer,barriers on the periphery of the semi-trailer are conveniently monitored, protective measures are taken when the semi-trailer is collided by the barriers, economic loss is reduced, and safety of related people is guaranteed as far as possible.