FIELD: railway engineering. SUBSTANCE: automobile and tractor construction, mainly to coupling devices for automobile and tractor trains with single-axle trailers. The proposed stabilizing coupling device for a single-axle trailer helps maintain the straight-line motion of the trailer and reduce the magnitude of its lateral deviations from external force influences. At the same time, the proposed device reduces the resistance to folding the trailer relative to the tractor when turning. This is achieved by installing between the trailer body and the tractor, coaxially with the traction lever in a vertical longitudinal plane passing through the middle of the axes of the running wheels of the tractor and the single-axle trailer, a stabilizing power hydraulic cylinder controlled by the distributor of the tractor's hydraulic system. In this case, the hydraulic cylinder is connected to the tractor and the traction lever, and the body of this hydraulic cylinder is attached to the tractor by means of a hinge, shifted forward along the transport train relative to the hinged fastening of the traction lever to the tractor, and the hydraulic cylinder rod is connected to the traction lever by means of a hinge, shifted backward along the transport train, regarding the hinged attachment of the traction lever to the tractor. EFFECT: proposed stabilizing coupling device of a single-axle trailer ensures the maintenance of the necessary stabilizing force moment acting on the traction lever relative to the articulated connection of the tractor with the traction lever, while the relationships of the kinematic elements of the proposed technical solution make it possible to reduce the force moment between the tractor and the trailer when turning transport train, which improves the turning conditions of the transport train. 1 cl, 2 dwg.