A reciprocating drag conveyor for fixed container detection system belongs to drag machine technical field, which comprises a driving device, a head pulley device, a frame and a tail tension device. The frame is connected with the head pulley device and the tail tension device, and the power of the driving device is transmitted to the head pulley device. Both sides of the head pulley device and the transmission shaft of the tail tension device are equipped with chain wheels embedded with dragging chains. The structural characteristic is that the dragging chains are arranged between the parallel upper and lower brackets connected with the frame, and the dragging chains are tensioned during the whole course to equal the chain lengths at upper and lower parts and realize free reciprocating transmission of the drag conveyor. Compared to prior art, the utility model can be used frequently and repeatedly at normal state, thus enhancing the efficiency of cargo/vehicle conveying and examination and enlarging application range.