A labyrinth sealing device for reducing gas intrusion is provided. A sealing bush is provided with a jet hole at the front of a tooth tip gap. The jet hole faces a tip of a corresponding sealing tooth. A gas flow injected by the jet hole suppresses hot gas flowing into the tooth tip gap. The sealing bush is provided with a first intercepting member at the rear of the tooth tip gap, and the sealing tooth is provided with a second intercepting member at the rear of the tooth tip gap. The first intercepting member hinders hot gas flowing against an inner wall of the sealing bush, and the second intercepting member hinders hot gas flowing against the sealing tooth, such that a part of the hot gas flows in a reverse direction and is violently mixed with subsequent hot gas.