The invention discloses an automatic sealing door of a sterilizer. The automatic sealing door comprises a door body. A sealing ring is arranged between the door body and a body. The sealing door comprises a drive device capable of driving the door body to rotate, a sealing device arranged between the door body and the body, and a lifting device capable of driving the door body to ascend and descend, wherein the sealing device comprises a locking tooth I and a locking tooth II. The locking tooth I is provided with protrusions and grooves sequentially in the length direction of the locking tooth I. The locking tooth II is provided with protrusions and grooves sequentially in the length direction of the locking tooth II. When the door body rotates to be closed, the lifting device lifts the door body firstly to enable the protrusions and the grooves on the locking tooth I and the locking tooth II to be engaged for passing, then the lifting device lowers the door body to enable the protrusions on the locking tooth I and the locking II to be overlapped, and then the door body is locked and sealed. The sterilizer can be started or stopped or sealed automatically, and has good sealing performance, and the problem that a sealing door in the prior art can not be opened or closed automatically is solved.