The invention discloses a fermentation container with a long-acting water sealing device. The fermentation container comprises a container body, wherein a container opening is formed in the container body; an opening edge as a water tank is arranged on the container opening; a cap covers the opening edge with water, so as to realize the sealing; a sealed water tank is arranged above the opening edge; a water outlet of the water tank is arranged in the opening edge; the height of the water outlet is lower than the upper edge of the opening edge. The fermentation container with the long-acting water sealing device provided by the invention utilizes the sealed water tank to supplement water in the opening edge of the container body; the long-acting stable water sealing is maintained; the operation of frequently adding the sealing water into the opening edge within a short period of time is not required; the invalid sealing caused by the evaporation of water in the opening edge can be avoided; the excellent anaerobic environment in the container body is maintained; the fermentation container does not need to be managed by the worker for a long time; the full anaerobic fermentation in the container body can be guaranteed; the fermentation quality is increased; the fermentation container can be widely applied to the industries of dairy products, beverage, bioengineering, pharmacy, fine chemical engineering, and the like.