The present invention relates to a self-locking nut which comprises a nut body and an elastic part, wherein the cross section of the elastic part is a hollow circular shape, the bottom side of the elastic part is fixed on the nut body, and the outer diameter of the bottom side is larger than that of the top; the top is provided with an opening, the size of which is equivalent to the large diameter of a screw hole of the nut body; and one or more rabbet(s) is/are arranged from the opening to the bottom side; the joint part of the bottom side of elastic part and the nut body is arc-shaped. The self-locking nut has fewer parts, easy installation and firm locking, so as to shorten the operation time, improve the working efficiency and enhance the fastness of a locking piece.