The invention discloses a shaft disassembling tool and a shaft disassembling method, and belongs to the field of mechanical shafts. The shaft disassembling tool comprises a fixing ring, mounting bolts, mounting nuts, jacking bolts and a tool shaft end clamping plate; the tool shaft end clamping plate is used for being clamped on the outer circumferential wall of a first end of a to-be-disassembledshaft, and mounting bolt threaded holes matched with the mounting bolts are formed in the tool shaft end clamping plate; the fixing ring is used for sleeving the first end of the to-be-disassembled shaft, the fixing ring abuts against the tool shaft end clamping plate, and the diameter of the inner ring of the fixing ring is larger than the diameter of the to-be-disassembled shaft; and mounting bolt mounting holes which corresponds to the mounting bolt threaded holes are formed in the fixing ring, and the mounting bolts penetrate through the mounting bolt mounting holes and the mounting boltthreaded holes to be in threaded connection with the mounting nuts. According to the shaft disassembling tool and the shaft disassembling method, the shaft disassembling tool is small in size, a largemounting space is not needed, the mounting shaft disassembling tool does not need to be lifted, meanwhile, the time consumption is short, so that the dismounting shaft efficiency is improved.