The sealed tank includes a tank body and a tank cover, with a circumferential groove on the joint surface between the tank cover and the tank body, and a sealing ring on the circumferential groove; The upper opening of the sealing ring is equipped with an outward opposite edge of the upper opening, and a gas hole is arranged on the opposite edge of the upper opening; The lower opening of the sealing ring is equipped with a hook, which matches the lower opening of the tank cover. After adopting the above structure, there are two seals between the tank body and the tank cover. The first one is sealed by the convex surface of the sealing ring, and the second one is sealed by the reverse side of the upper opening. The lower opening hook can ensure that the sealing ring is installed firmly, not deformed, and prevent hands from being scratched by the cover opening; It has the advantages of simple and reasonable structure, convenient processing, high production efficiency, good sealing effect, and durability.