Method for hoisting ultrahigh spud leg by stock gantry crane

The invention discloses a method for hoisting an ultrahigh spud leg by a stock gantry crane. A gantry crane, a lifting hook, a spud leg, a sand box, a supporting plate, a water tank, speed reduction motors, rotary arms, balancing weights, a lifting lug and a slide plate are included. The method comprises the following steps that the supporting plate is firstly installed on the lower part of the spud leg, and is provided with the sand box and the water tank; the speed reduction motors are installed at two sides of the water tank, rotation shafts of the speed reduction motors are provided with the rotary arms, and the rotary arms are provided with the balancing weights; the gantry crane is driven slowly, the lifting hook is suspended on the lifting lug, thelifting lug is welded to the middle of the spud leg, so that the spud leg can be pulled highly; a pulley of the gantry crane is close to the slide plate, the lifting hook and the sand box are locked tightly by a rope so as to prevent falling; thelifting hook of the gantry crane is lifted up slowly until the lower part of the spud leg is higher than a whole ship body, and then the gantry crane is driven to a designated position for butting joint; by establishing on land and constructing upward integrally and intensifying the structure, the gantry crane has the integral hoisting condition so as to complete the one-timehoisting finally, so that 20% of time by integrally constructing upward in constructionis shortened.