The mobile girder rail gantry crane consists of the main beam, rigid and flexible door legs, operating trolley, lifting mechanism, cart operating mechanism, electrical system, operating cab, etc. According to the yard operation process, the cantilever can be extended in the direction of the single door leg or the double door leg to become a single cantilever or double cantilever model, and if it is not extended, it will be a non-cantilever model. According to the location, container storage and transportation process, and loading and unloading vehicles (container trucks or railway vehicles), confirm the selection of different structural methods without cantilever, single cantilever, and double cantilever.