The utility model discloses an automatic bolt, include: the base, including relative roof and diapire and the perisporium of connection between roof and diapire, the intercommunication has first through -hole between roof and the diapire, can stretch out the diapire outside and return the rotor that contracts in first through -hole through first through -hole, locate roof one side, the bolt pole is in the movable fixed block of pegging graft on the roof, locating roof one side and locating the driving medium between rotor and the bolt pole, under the rotor returned the state that contracts in first through -hole, the driving medium promoted the outside that the bolt pole stretches out the perisporium, the spring on the bolt pole is located to the cover, and under the reset state of spring, the bolt pole returns to contract and promotes the rotor to the inboard and driving medium of perisporium and stretch out the diapire. This kind of automatic bolt passes through the linkage between rotor, driving medium and the bolt pole, can realize the automatically move of bolt pole at the in -process that opens and shuts of bivalve door, can open the bolt on the bivalve door more conveniently, makes the process of opening the door more swift, and automatic bolt is more reliable to the locking of bivalve door.