Compared with the traditional bogie wheelset structure, the gauge-changeable bogie wheelset needs a set of unlockinglocking device for track gauge change. The effect of the device is to realize the unlocking before the wheel slip and the locking during operation. It is a key component that directly influences the change of the inner distance of the wheelset and ensures the safety of the train. The structure and action principle of the unlocking-locking device of the bogie with high-speed gauge-changeable EMUs was introduced, and the force state of the device during operation was analyzed. At the same time, the strength analysis and life calculation of the device were performed. Analysis and calculation results showed that the unlocking-locking device met the design requirements.