Container loading and unloading method and elevation type double-layer girder shore crane container loading and unloading system

The invention discloses a container loading and unloading method and an elevation type double-layer girder shore crane container loading and unloading system. The loading and unloading system comprises a yarn crane, a ferry crane and a shore crane, the yarn crane is connected with the shore crane through the ferry crane, the shore crane comprises a framework a, an integrated elevation girder and a framework b, and the framework b is arranged above the framework a. The integrated elevation girder comprises an upper-portion beam, a lower-portion beam and a girder locking device. The framework b comprises an elevation mechanism and a gantry, and the elevation mechanism is arranged on the gantry. Compared with the prior art, the integrated elevation girder can move up and down on the frameworks; due to the fact that the integrated elevation girder is provided with the girder locking device, the integrated elevation girder can be locked at a proper position through the girder locking device; the height of the integrated elevation girder is changed to adjust the hoisting height of a container, the distance between the integrated elevation girder and the container is kept unchanged, the time for carrying the container is effectively shortened, the efficiency of carrying the container is greatly improved in a large degree, and the handling capacity of a port is improved.