The invention relates to a self-locking device used for an insulator chain under a non-natural movement track. The self-locking device comprises a ball head assembly and a bowl head assembly. The ball head assembly comprises a ball head and a ball head rod. The diameter of the ball head is larger than that of the ball head rod. The bowl head assembly is of a hollow cylindrical structure with enclosed upper and lower parts. A ball head inlet-outlet is arranged in the lower part of one side of the bowl head assembly. A translation groove where the ball head rod is capable of moving is arranged in the upper part of the bowl head assembly. The width of the translation groove is smaller than the diameter of the ball head. A limiting column is arranged in the center position of the lower bottom face in the bowl head assembly. A limiting groove is arranged in an opposite side, to the ball head inlet-outlet, of the limiting column. The self-locking device is good in locking effects, not liable to falling off, and convenient to install under the non-natural moving track.