The invention provides a dog-bone joint beam end buckling constraining device. The device comprises constraining cover plates (1), constraining U-steel (2), filling plates (3) arranged between the constraining cover plates and the constraining U-steel, and connecting bolts (4), wherein the constraining cover plates (1) are arranged on the outer sides of upper and lower flange weakening parts (7-1) at the ends of a steel beam (7) provided with a dog-bone joint; the constraining U-steel (2) is arranged on the portions, corresponding to the two sides of a web, of the flange weakening parts; and the connecting bolts (4) are used for connecting the constraining cover plates, the constraining U-steel and the filling plates to form the complete constraining device. When an earthquake occurs, the beam end flange weakening parts yield in advance of other parts and components, earthquake energy is dissipated through the hysteretic characteristic, and by adoption of the constraining device, press on the beam end flange weakening parts and large-amplitude buckling possibly occurring outside the plane of a steel plate when the corresponding web is pressed and sheared can be limited, shortening of the fatigue lives of the flange weakening parts and degradation of joint rigidity and strength are prevented, the steel beam (7) in a joint area is protected against complete buckling outside the plane, the fullness of a hysteretic curve is ensured, and the joint deformation capacity and ductility and the lateral stability of the beam are improved.