The invention relates to the field of locomotive repair, in particular to a device for positioning a rubber joint in a locomotive motor boom in a press fitting way. The device comprises a lower clamping plate, an upper clamping plate, a connecting plate, a lower plate hole and an upper plate hole, wherein the lower clamping plate and the upper clamping plate are positioned on both sides of the connecting plate respectively, thereby forming a Z shape as a whole; the lower plate hole is formed on the lower clamping plate; the upper plate hole is formed on the upper clamping plate; the shapes of the lower plate hole and the upper plate hole are consistent with the shapes of joint ends; the vertical distance between the lower plate hole and the upper plate hole is equal to the distance between two joint ends after completion of mounting. By adopting the device, the mounting procedure is simplified, operating personnel can adjust the mounting accuracy conveniently, and the machining efficiency is increased.