The invention discloses a detachable cyclic utilization device controlling floating of a light block filling internal mold. The device comprises a screw, a round ring, and a square timber. One end of the screw is provided with threads. An umbrella-type clamp and a nut are sleeved on the threads. The other end of the screw is welded with the round ring. The square timber passes through the round ring. In construction, after reinforcing steel bars of a top plate are bound and inner molds are arranged, a manufactured screw is placed in the gap between two inner molds, through a sleeve, the screw passes through a template and is connected with a steel pipe which is used as a main keel, and the screw is fixed through the umbrella-type clamp and the nut. The other end of the screw makes the square timber pass through the round ring and tightly press on the upper surface of the inner mold, so as to achieve of controlling displacement and floating of the inner mold. The device does not independently bind and locate the hollow inner mold blocks by steel wires, so a construction procedure is reduced, and construction cost is saved. After concrete pouring is completed, bolts can be recycled, preventing defects that a roof leaks caused by rusting of tips of iron wires, and saving project cost.