The invention discloses a ball valve with zero friction between a valve seat and a ball. The technical scheme is characterized in that the ball valve comprises a valve body with a valve cavity, the ball positioned in the valve cavity, a valve rod in linkage with the ball and the valve seat arranged between the valve body and the ball. The valve rod is partially exposed outside the valve body and provided with a valve seat cavity and an air inlet which is communicated with the valve seat cavity and allows air to enter, the valve seat is embedded into the valve seat cavity and in clearance fit with the same, and an elastic part which is capable of driving the valve seat to slide in the direction opposite to one side of the ball to disable the valve seat to contact with the ball is arranged in the valve seat cavity. When the ball is closed, external air can enter the valve seat cavity through the air inlet, the valve seat overcomes acting force of the elastic part to slide towards one side of the ball under the action of air pressure, so that sealing faces of the valve seat and the ball can be closely attached to enable the ball valve to be reliably sealed. When the ball needs to be opened, air in the valve seat cavity is exhausted, and the elastic part drives the valve seat to slide opposite to one side of the ball to disable the valve seat to contact with the ball, so that zero friction is realized.