The utility model relates to a radiation scanning detection device for small and medium size vehicle. The device comprises a door frame, a radiation source, a detector, a support platform, a conveyor support, a cycle dragging unit, a wheel guiding unit, and a suspension bridge unit. The beneficial effects of the device are that, an arrangement mode of a top radiation source and a U-shaped detector is adopted, thereby achieving flat radiation detection of a vehicle, and effectively improving image quality; a high sensitivity detector is adopted, the image resolution can reach the grade of parcel detection, and recognition of prohibited items such as guns, cutters, exploders, etc. by a security check inspector is facilitated; a double energy detection technology is adopted to detect the characteristics of materials of the items in the vehicle, thereby facilitating the security check inspector to recognize flammable and explosive dangerous items; trundles and foundations are designed for a vehicle conveying device and an inspection channel, thereby facilitating installation debugging and movement of the device, achieving non-fixed installation to the ground, and preventing damage upon the on-site ground.