The invention belongs to the technical field of bridge damping and provides a cantilever type damping device for a simply supported girder bridge of a railway. The cantilever type damping device comprises a damping tenon (13) and a connecting sleeve (2) fixedly connected at the bottom of a beam body (1), the upper end of the damping tenon (13) is connected with a knuckle bearing (10), and the outer circumference of the outer ring of the knuckle ring (10) is a cylindrical surface matched with the inner wall of the connecting sleeve (2); the knuckle bearing (10) is arranged in the connecting sleeve (2), the outer circumference of the knuckle spring (10) is in slide fit with the inner wall of the connecting sleeve (2); a beam embedding component (8) connected with the connecting sleeve is embedded in the beam body (1), and pier embedding components (12) connected with the damping tenon are embedded in a pier (6). By the cantilever type damping device, contact stress of the force transmission sleeve and the knuckle bearing is reduced, and service life of the damping device is prolonged.