A gauge-changing wheelset, comprising an axle, a pair of wheels, further comprising a pair of axle sleeves, an outer sleeve and a linkage mechanism (60, 70, 80), wherein an outer circumference of a first end of each axle sleeve is provided with a wheel mounting base, an outer circumference of a second end of each axle sleeve is provided with a section of an outer spline extending along an axial direction of the axle sleeve, an inner circumference of the second end of each axle sleeve is provided with a section of a first non-self-locking thread, a pair of the first non-self-locking threads of the pair of axle sleeves have opposite directions of rotation, and the pair of wheels are fastened on the wheel mounting bases of the pair of axle sleeves; the axle is provided with two sections of second non-self-locking threads at intervals, each second non-self-locking thread forming a non-self-locking thread pair with the first non-self-locking thread; the wheels are mounted on the axle through the axle sleeves, the first non-self-locking thread is fitted and connected with the second non-self-locking thread, and a part of the axle between the pair of second non-self-locking threads is provided with at least one first raceway circumferentially disposed around the axle; the outer sleeve is sleeved outside the axle, an inner circumference of the outer sleeve is provided with a second raceway corresponding to and being snap-fitted with the first raceway to form a rolling space in which a rolling element matched therewith is mounted such that the outer sleeve is rotatably connected outside the axle, and an inner spline matched with the outer spline on the axle sleeve is provided on both axial sides of the second raceway inside the outer sleeve and located at a predetermined distance from the second raceway; and the linkage mechanism is mounted between the axle and the outer sleeve for locking or unlocking rotation of the outer sleeve relative to the axle; and when the rotation of the outer sleeve relative to the axle is unlocked by the linkage mechanism and the wheels are in an unloaded state, the pair of wheels are pushed to rotate synchronously to move closer to each other or away from each other, so as to change the gauge. wherein an outer circumference of a first end of each axle sleeve is provided with a wheel mounting base, an outer circumference of a second end of each axle sleeve is provided with a section of an outer spline extending along an axial direction of the axle sleeve, an inner circumference of the second end of each axle sleeve is provided with a section of a first non-self-locking thread, a pair of the first non-self-locking threads of the pair of axle sleeves have opposite directions of rotation, and the pair of wheels are fastened on the wheel mounting bases of the pair of axle sleeves; the axle is provided with two sections of second non-self-locking threads at intervals, each second non-self-locking thread forming a non-self-locking thread pair with the first non-self-locking thread; the wheels are mounted on the axle through the axle sleeves, the first non-self-locking thread is fitted and connected with the second non-self-locking thread, and a part of the axle between the pair of second non-self-locking threads is provided with at least one first raceway circumferentially disposed around the axle; the outer sleeve is sleeved outside the axle, an inner circumference of the outer sleeve is provided with a second raceway corresponding to and being snap-fitted with the first raceway to form a rolling space in which a rolling element matched therewith is mounted such that the outer sleeve is rotatably connected outside the axle, and an inner spline matched with the outer spline on the axle sleeve is provided on both axial sides of the second raceway inside the outer sleeve and located at a predetermined distance from the second raceway; and the linkage mechanism is mounted between the axle and the outer sleeve for locking or unlocking rotation of the outer sleeve relative to the axle; and when the rotation of the outer sleeve relative to the axle is unlocked by the linkage mechanism and the wheels are in an unloaded state, the pair of wheels are pushed to rotate synchronously to move closer to each other or away from each other, so as to change the gauge.