The invention discloses a fastening device of a bayonet circular electric connector under big impact vibration. The objective of the invention is to solve the technical problem of poor reliability ofcurrent fastening devices. The device comprises a fastening substrate, a fastening plate, an insertion plate and a fastening screw. The device is capable of fastening a plug and a socket of a bayonetcircular electric connector under big impact vibration. The fastening substrate sleeves the outer edge of a square disc installation plate of a motor socket. The same fastening screw is used on the fastening substrate and the motor socket. After a bayonet plug is rapidly installed, the fastening plate is installed on the tail accessory of the plug. The insertion plate is inserted in the opening end of the fastening plate. The fastening screw is used for connecting the fastening plate, the insertion plate and the fastening substrate. According to the invention, the fastening device is used forthe bayonet circular electric connector, so reliable connection of the bayonet circular electric connector under the big impact vibration is achieved.