The invention relates to the field of variable gauges for rail vehicles, and discloses a locking mechanism for a variable gauge wheel set and a bogie. The wheel set comprises wheels, an axle and locking mechanisms. Each locking mechanism includes a fixed sleeve, a locking pin, a mitigation sleeve and an unlocking disc. The wheels are slidably arranged at the two ends of the axle, the locking mechanisms are disposed on the inner side axle of the wheel, and by pushing the unlocking disc to drive the locking pin to move upwards, the fixed sleeve is unlocked with the mitigation sleeve. Therefore,the wheels are locked or unlocked conveniently, to achieve the variable gauge. The locking mechanism can achieve locking or unlocking reliably, and thus the variable gauge of a train can be achieved conveniently and reliably.