The invention discloses a broken rope self-locking device. A gear support body is arranged in a shell; a vertical hole is formed in the lower part of the center of the gear support body; conical holes which are large at the upper ends and small at the lower ends are formed in the upper part of the vertical hole; a groove is formed in each of the left side and the right side of the gear support body; two gears are arranged in the left groove and the right groove of the gear support body; left and right taper pipes which are opposite to and separated from each other and are large at the upper ends and small at the lower ends are arranged in the conical hole in the upper part of the gear support body in a sliding fit way; two pressure springs are arranged between the upper end face of each taper pipes and a top plate; a swinging rod is arranged in each of the left and right grooves in the upper part of the gear support body; the lower ends of the swinging rods are arranged in radial grooves which are uniformly formed in the inner peripheral surfaces of the gears; pin holes which are in sliding fit with pins are formed in the outer side walls of the left and right separated taper pipes; the two ends of a pulling rope are connected with the upper ends of the swinging rods and the outer ends of the pins respectively. The broken rope self-locking device has the advantage that safety accidents occurring when steel wire ropes are broken are avoided.