The invention discloses a spherical valve overhaul sealing control method which is characterized in that the spherical valve overhaul sealing control method comprises the following steps that a, the area of an opening cavity of a movable sealing ring in a spherical valve, the area of an upstream high pressure cavity, the area of an upstream input cavity and the area of a downstream pressure cavityare set; b, normal overhaul is carried out, a water turbine is shut down, a valve body of the spherical valve is fully closed through a servomotor, the movable sealing ring is put in, water in a downstream pipeline of the spherical valve is drained, and the movable sealing ring is pressed under the pressure of the upstream input cavity and the pressure of the upstream high pressure cavity; c, extreme overhaul is carried out, the upstream input cavity is subjected to pressure loss, the opening cavity is subjected to pressure buildup, and the movable sealing ring is pressed; and d, after the overhaul, a by-pass line is opened for carrying out pressure balance on the upstream side and the downstream side of the spherical valve. The free input and withdrawing of overhaul sealing in a normal overhaul state can be realized, the situation that the overhaul sealing is not opened during misoperation can be guaranteed, the safety of a maintainer is ensured, and the spherical valve overhaul sealing control method has the characteristics of convenience in operation, safety and reliability.