Nut locking device

The utility model relates to a nut locking device which comprises a circular nut (1) and fastening bolts (3), wherein two fastening bolts (3) are arranged on the circular nut (1) and two moveable blocks (2) are arranged in the positions of the fastening bolts (3) of the circular nut (1). The nut locking device has a simple structure, is convenient to operate and has a good anti-loosening effect.