The invention discloses a pin shaft dismounting method and belongs to the technical field of mechanical equipment maintenance. The method comprises the following steps of: Step 1, dismounting a component for fixing the pin shaft, Step 2, forming a through hole in the center of the pin shaft along an axis by using a hot working method, Step 3, cooling the pin shaft, and Step 4, dismounting the pin shaft from a pin hole by using a mechanical and hydraulic pin puller or a heavy body impact method. The method only damages the pin shaft, does not cause scrap of a connecting piece or influence the precision of the pin hole, and enables the pin hole to meet secondary assembly requirements in an implementation process. In addition, the method is applicable to the dismounting of the pin shaft in many environments and many forms. The method is simple to operate and low in labor intensity and dismounting expense, dismounts the pin shaft conveniently, reduces labor cost and improves production efficiency.