YQ2 Oil Lubrication Stern Shaft Sealing Apparatus is the key equipment of large ship propulsion system, and its sealing performance directly determines whether the ship propulsion system can work normally. It is composed of a front sealing device and a back sealing device. The front sealing device is installed in the cabin where the stern shaft passes through the hull and is used to prevent the lubricating oil in the stern tube from leaking into the cabin. The back sealing device is installed on the stern shaft outside the hull to prevent sea water from entering the stern shaft tube and to prevent oil leakage in the tube.