Lifting large gantry cane

The utility model provides a new style jacking type large gantry crane and the disassembly and the assembly process thereof, which solves the problem that large hoisting equipment which is used in fluidity working places, such as mining areas, oil extracting areas, etc., is difficult to transport and install. Structural members of the crane portal frame are detachable, and all the structural members adopt weight limiting and money-shaped limiting design; jacking support bases which are used for loading and unloading are arranged on a main beam, an upper beam, each segment of the door leg, and a steel structure of a lower beam; the door leg is composed of eleven sections which are connected in series, and a flange for jacking an oil cylinder is adopted to complete that each section of the door leg is connected in series with the flange; the main beam, the upper and the lower beams also adopts the jacking to complete the installation without the large hoisting equipment. Only a jacking oil cylinder is adopted to install a large gantry crane as high as 18 meters with the elevating capacity of 300 tons, and the utility model plays an important role on construction in mining areas and oil extracting areas with large fluidity.