The invention relates to a large-medium-caliber hard sealing long-service-life ball valve, which comprises a valve body, a valve rod, a valve cover and a ball body, wherein the valve body is in ball-shaped arrangement, in addition, medium flow passages are arranged at two ends of the valve body, the valve cover is fixedly connected with the valve body, the valve rod passes through the valve cover to realize the linkage arrangement with the ball body, the valve rod is provided with outwards projected steps, the steps are arranged at one side of the valve cover corresponding to the ball body, an accommodating cavity for accommodating sealing materials is arranged between the valve cover and the steps, sealing materials are filled in the accommodating cavity, the other side of the valve cover relative to the steps is provided with a tight combining screw nut matched with the valve rod, and a butterfly spring is clamped and arranged between the opposite surface of the valve cover and the wall surface of the right combining screw nut corresponding to one side of the steps. The large-medium-caliber hard sealing long-service-life ball valve adopting the technical scheme has the effect that the service life of the ball valve is greatly prolonged.