The stern shaft sealing device is one of the important parts of the ship shafting. Its performance directly affects the operation of the ship, and also plays a very important role in preventing the stern shaft lubricating oil from polluting the marine environment. Therefore, it is extremely necessary to study the stern shaft sealing device. On the ship where the author is working, the engine room stern shaft seal oil tank gave a high level alarm when sailing in strong wind and waves. After inspection, it was found that the poor stern shaft seal caused seawater to leak into the seal oil chamber, causing the seal oil tank to be high and emulsified. There are two common cases of leakage of sealing oil of ship's stern shaft: first, in strong wind and wave weather, the draft of ship's stern is small, and severe vibration of the hull will cause poor sealing of the sealing device; ...