The utility model discloses a self-lock device for pulling timber piles, and belongs to the field of foundation treatment construction machinery. The device comprises a steel sleeve, self-lock toothed plates and pin shafts, wherein the two self-lock toothed plates are connected with the steel sleeve through the two pin shafts. The self-lock device is reasonable and simple in structure, easy to produce and manufacture, high in construction efficiency, capable of being reformed according to the diameter of the timber piles, low in cost, and capable of effectively and rapidly pulling out underground timber piles within 15 cm in pile length and less than 350 mm in edge length.