The ball mill trunnion is located at both ends of the ball mill cylinder and plays the role of supporting and connecting the mill cylinder. Two ball mill trunnions are installed at both ends of a ball mill, one is the feed trunnion, which is the passage for the material to be transported into the cylinder, and the other is the discharge trunnion, through which the ground material is sent out. The trunnion bearing supports the ball mill trunnion and drives the trunnion to rotate. A trunnion liner is installed in the trunnion of the ball mill to slow down the impact of raw materials on the ball mill trunnion wall.