A multi-stage watertight chamber is provided in this invention. The multi-stage watertight chamber comprises a first rotary seal, a second rotary seal, a first housing, a second housing, and an integrated shaft. The first and second rotary seals withstand external pressure to make sure watertight status is achieved when the integrated shaft rotates. The first housing forms a first watertight chamber. The integrated shaft protrudes through the first housing via the first rotary seal. The second housing is placed outside and adjacent to the first housing and forms a second watertight chamber. The first watertight chamber contains devices that must be isolated from liquid outside the first and second housings. The second watertight chamber is used to store water seeped through the second rotary seal and avoid causing damage directly to components and apparatus inside the first watertight chamber.