The invention relates to a high-temperature over-speed test change-over device for a cantilever turbine disc. The high-temperature over-speed test change-over device includes a turbine disc connection component (1), a positioning block (2), an M10 hexagon socket head cap screw (3) and C type flat keys (4). The high-temperature over-speed test change-over device is mainly used for the over-speed fatigue test of the rotor of the cantilever turbine disc under a high-temperature state. With the device adopted, the positioning, butt joint, fastening and torsion transmission of the driving shaft of a test bed and the turbine disc can be realized. According to the design of the device, requirements for the strength of a high-temperature structure and the rotational inertia of a rotary shaft system are fully considered. The device of the invention has the advantages of light weight, excellent positioning effect, high temperature resistance (600 DEG C), looseness prevention and the like. Under a high speed (35000r/min) state, the device is high in stability and excellent in test effect. The device is provided with a de-weighting belt, so that dynamic balance de-weighting before a test can be facilitated.