The invention discloses a secondary buffering device for a coupler, belonging to the technical field of vehicle. The secondary buffering device for a coupler is provided with at least one pair of first through holes symmetrical with each other on a baffle I and a baffle II of a rear draft lug and at the positions corresponding to cavities; the secondary buffering device for a coupler further comprises a buffering baffle I, a buffering baffle II and buffering joints having equal quantity with the first through holes, wherein the buffering baffle I and the buffering baffle II are connected with the buffering joints via the first through holes respectively. The secondary buffering device for a coupler is tightly attached to the rear seat of the original buffer box of vehicle and is not separated from the same during application process, thereby eliminating idle stroke existing when the coupler of railway wagon is converted to impact working condition from traction working condition; and proper buffering force is acted, thereby prolonging the service life of buffering device for coupler.