The invention discloses flying dust preventing equipment for building perforation. The equipment comprises a plastic transparent hood and a first telescopic tube, wherein a plastic seal ring is arranged on one side of the plastic transparent hood, elastic telescopic cloth is arranged on the other side of the plastic transparent hood, a plastic dust outlet tube is arranged on the hood body, close to the plastic seal ring, of the plastic transparent hood, a connecting tube is arranged on the side, far from the plastic transparent hood, of the elastic telescopic cloth; two elastic telescopic units are formed by the first telescopic tube, the second telescopic tube and a reset spring to fix the relative positions of the plastic seal ring and the connecting tube, so that the dustproof performance of the plastic transparent hood and the elastic telescopic cloth between the plastic seal ring and the connecting tube during use is ensured, and meanwhile, the plastic transparent hood does not affect the observing view of a perforation operator; the plastic seal ring is in tight contact with a wall body through the two elastic telescopic units; and a dust storage bag and the plastic transparent hood are mounted and detached conveniently through the plastic dust outlet tube and a connector.