The invention discloses an automatic unhooking device of a subinclined shaft lower yard. The automatic unhooking device is characterized by comprising unhooking rack fixing beams. An unhooking rack is fixed by the two unhooking rack fixing beams. A hanging ring moving slideway is arranged in the unhooking rack. A hanging ring with a pulley moves in the hanging ring moving slideway. A hook is connected with a connecting pin through a ring chain. The unhooking device further comprises a ring type connecting device connected through a lifting steel wire rope. The automatic unhooking device has the advantages that automatic unhooking is achieved, labor intensity of workers is reduced, unhooking time is reduced, winch lifting capability is increased, and the device is simple in structure, safe and reliable, and convenient to mount and manufacture.