The invention provides an open gear sealing device which comprises a cover body used for containing an open gear pair. The cover body is provided with open pores. The open pores are arranged coaxially with open gears in the open gear pair, and the open pores penetrate through the cover body. An annular sealing strip is arranged on the inner wall of the cover body. The sealing strip is provided with at least two annular teeth concentrically arranged on one end face of the sealing strip. The sealing strip and the open pores are arranged coaxially. The annular teeth are embedded in annular grooves formed in the end faces of two sides of one open gear so that the tooth form parts of the open gear pair can be sealed. According to the open gear sealing device, the open gears are contained in the cover body, the sealing strip arranged on the cover body is provided with the annular teeth, the annular teeth are matched with the annular grooves formed in the end faces of the corresponding open gear, and therefore the tooth form parts of the open gears can be reliably sealed, and sludge is prevented from entering the tooth form parts of the open gears.