The invention relates to a motorcycle body structure. A motorcycle comprises a frame and a body cover; a steering handle is provided on a frame head pipe, the head pipe is connected with a down pipe portion, the body cover overlies the outside of the frame, the body cover has a front panel and a knee cap, the knee cap is provided with a storage portion, the storage portion has a cover plate which seals the storage portion, the down pipe portion of the frame has a frame production number, and an inspection window is arranged in the storage portion and corresponding to the frame production number; and the frame production number is printed on the down pipe portion, which is completely wrapped with the knee cap and the front panel, the knee cap and the front panel form a sealing space in the down pipe portion to avoid pollution of ground waste water or dust to the down pipe portion, the storage portion is disposed on the knee cap, the inspection window is arranged in the storage portion and corresponding to the down pipe portion, the frame production number can be inspected through the inspection window by simply opening the cover plate of the storage portion, and thus the convenience of inspecting the frame production number is improved.