The utility model relates to a bridging plug device based on expandable casing, including inflation awl, bridging plug body, sealed component and the center tube of hanging, wherein: the bridging plug body is the reducing expandable casing nipple joint of one section expandable, and big footpath end is the expandable casing after expanding, and the path end is unexpanded expandable casing, the center pipe box is originally internal at the bridging plug, and the inflation awl is connected in the center tube lower part, and the conical surface that the inflation was bored forms conical surface sliding sealed fit with the reducing conical surface of bridging plug body, the sealed component that hangs solidifies on the path end expandable casing of bridging plug body, hugs closely behind its inflation to form permanent sealing between bridging plug body and outer sleeve pipe. Its technological advantages lie in that bridging plug and packer are integrative, structure, simple process, and the layering is reliable, cheap cost.