The utility model discloses a movable rail including two steel rails, one of the steel rails is installed on a plurality of steel rail gauge-changing devices as a movable steel rail, a sliding component is welded on a base plate of the steel rail gauge-changing device, a sliding opening is opened on a top surface of the sliding component, a bolt inserting opening is respectively opened on two ends of the sliding opening. A plurality of groups of dowel holes are opened on the sliding opening, two dowel holes in each group of dowel holes are symmetrically arranged on two sides of the sliding opening. The movable steel rail is arranged on the sliding component, base sides of two sides of the movable steel rail are respectively pressed downwards by end part of a fastener which is pressed by bolt joint of a bolt and a nut after the bolt slides into the sliding opening through a bolt inserting opening and passes through the fastener and is connected with the nut by the mode of screw cap facing downside; dowels are connected by pins in each dowel hole on a lateral base side of an adjacent moveable steel rail. The steel rail gauge-changing device of the utility model can change the steel rail gauge at a horizontal transverse direction, thereby the production and maintenance requirement of domestic and overseas locomotives and vehicles with a plurality of track gauges is sufficed.