The invention provides a nut automatic feeding and discharging system, a nut necking machine and a nut necking method and relates to the technical field of self-locking nut process. The nut automatic feeding and discharging system comprises a feeder, a conveying track, a first conveyor and a second conveyor. A discharging opening of the feeder cooperates with a feeding port of the transportation pathway to transport the nut to the transportation pathway. The transportation pathway comprises a first pathway, a second pathway and a third pathway. The first transporter comprises an air cylinder. One nut is sent as the air cylinder works a time. The second transport comprises a belt. Multiple driving levers are disposed on the belt in an interval mode. As driven by the belt, the driving levers are used for prodding the nut in the discharging opening of the second pathway and carrying the nut to next station for feeding process of the nut; the driving levers are used for prodding and taking away the nut which is processed on the next station for the blanking of the nut. The nut automatic feeding and discharging system needn't manual feeding and blanking and has the advantages of stronger adaptability, time saving and labor saving.