One way sealed fully enclosed knife gate valve is a structure in which the gate is fully enclosed in the valve chamber for opening and closing sealing. It is suitable for installation under sewage tanks, pipelines where the valve body is immersed in liquid, or pipelines where valves are installed underground and the pressure is greater than or equal to PN10 The sealing structure is achieved by closing the gate and moving it downwards until the inclined surface at the bottom of the gate matches the wedge block under the valve body, so that the gate is tightly attached to the sealing surface of the valve seat, thus achieving a sealing effect The upper semicircle of the gate plate is equipped with a slope wedge block and a slope wedge block on the inner cavity of the valve body. The PTFE guide ring is used to smoothly open and close with the gate plate plane, making the seal more reliable. The circular packing on the valve stem is equipped with dual Y-shaped and O-shaped sealing rings and a reverse sealing structure, which can ensure that the packing can be replaced online when the gate is fully opened, ensuring that the upper valve stem seal of the valve does not leak for a long time.