The invention relates to the field of train variable gauges, discloses a locking mechanism for a variable gauge wheel set and the variable gauge wheel set. The variable gauge wheel set comprises a bearing sleeve and a locking rod, wherein the inner circumference of the bearing sleeve is provided with an annular positioning boss dividing the inner circumferential surface of the bearing sleeve intoa locking working surface and a press-fit working surface. The two opposite sides in the radial direction of the locking working surface are respectively provided with a set of gauge change grooves, each set of gauge change grooves comprises a plurality of gauge change grooves formed at the axial interval, and through notches are formed in the locking working surface below the two sets of gauge change grooves. The locking rod comprises two symmetrical locking pins and unlocking rods hinged to the two locking pins. The two locking pins are respectively inserted into a single gauge change grooveof the corresponding group to achieve locking, the unlocking rods extend out of the bearing sleeve from the notches and enable the locking pins to be separated from the current gauge change grooves under the external force to achieve unlocking. The locking mechanism can achieve the locking and the unlocking reliably to meet the variable gauge requirement of a train.