The gantry crane is generally to be classified according to the structure of the mast, the form of the main beam, spreader form. Generally used for the port. Full gantry crane at the door frame structure (a): the main beam without overhang, the car in the main span. (B) semi-gantry crane: outrigger height difference, according to the civil requirements for use of the venue. The double cantilever gantry crane (c): The most common form of a structure, its force structure and the effective use of the site area are reasonable. The single cantilever gantry crane (d): This structure is often due to the restrictions of the venue has been chosen.