The invention provides a unidirectional plug valve, comprising a valve body, wherein a valve plate is arranged in the valve body, and a through hole is formed in the middle of the valve plate. The unidirectional plug valve is characterized in that a baffle is hinged at one side of the valve plate, the diameter of the baffle is greater than that of the through hole, the other side of the valve plate is provided with a cock cone matched with the through hole, the cock cone is connected with a valve rod, a cock pressure releasing thread sleeve is arranged on the valve rod, and the cock pressure releasing thread sleeve is connected with a boss of the valve body by screw. According to the invention, the unidirectional plug valve can effective prevent backflow in occasions with strict requirement on prevention of medium countercurrent, and is convenient to install and control and reliable and steady in work.