Full trailers are generally the frame, body, traction devices, steering, suspension, travel system, braking system, signalling systems and other components. Straight upper wing surface of beam longitudinal beam of the frame is straight. Its advantage is that trailer flat cargo floor, simple technology, high ground clearance, longitudinal good. Heavy duty flatbed trailer in order to meet its requirements and structure. Frame consists of main beams and cross beams, support beams and beam components. Vehicle load through the beams between the supporting beams, suspension, wheels, axle and wheel to the ground. The frame girder, support beams and beam of box section welded pieces, has greater torsional rigidity. Connect beams stretched out to the side of the main beam, welded I-section structure with variable cross-section, with high lateral bending strength. Frame girder height of larger size, and downward, frame without increasing the height of domestic trailer conditions, improved the frame longitudinal bending strength. The support beams below install the suspension dial mechanism is arranged in order to achieve all-wheel steering.