Tool for assembling transmission shaft

The invention discloses a tool for assembling a transmission shaft. The tool comprises a tube of which the external diameter is matched with the internal diameter of a shaft hole of a differential mechanism, and a tube edge which extends from the outer end of the tube to the periphery and is used for preventing the tube from falling into the shaft hole, wherein the tube is provided with a first notch which penetrates in the axial direction, and a protective layer used for preventing the tube from scratching an oil seal located in the shaft hole is arranged on the peripheral surface of the tube; and the tube edge is provided with a second notch which is communicated with the first notch. When a half shaft is mounted in the shaft hole of the differential mechanism through the tool, the oil seal in the shaft hole cannot be damaged.