The present invention discloses a seat folding mechanism, and comprises a back support rod, two connecting rods, two front support feet, a locking hook and a lock. Two ends of the back support rod are locked on the locking hook by the lock, and are simultaneously connected with the front support feet through the two connecting rods; two ends of the back support rod are folded to form a similar U shape; the lock is welded on the bottom of the U-shaped end; the locking hook is fixed on the vehicle floor by a bolt; the front support feet are also fixed on the vehicle floor by a bolt, and are provided with a wind spring; one end of the wind spring is fixed on the front support feet, and the other end is connected with a pin which is connected with the back cushion of the seat. The back support rod, the two connecting rods, the two front support feet and the back cushion of the seat form 4 link mechanisms; thus the back support rod can automatically draw back in the folding process; the operation is convenient and labor-saving; and the seat folding mechanism can effectively increase the luggage space of the whole vehicle.