The utility model discloses an automatic balance adjusting and locking device for an oil pumping unit. Balance box, a mounting box is fixedly connected between the two sides of the inner wall of the balance box; one side of the mounting box is fixedly connected with a supporting plate; the top of the supporting plate is fixedly connected with a motor; a rotating rod is fixedly connected to an output shaft of the motor, one end of the rotating rod penetrates through the mounting box and extends into the mounting box, a driving gear is fixedly connected to the surface of the end, extending intothe mounting box, of the rotating rod, and a rolling wheel is fixedly connected to the end, located in the mounting box, of the rotating rod. The utility model discloses an automatic balance adjustingand locking device for an oil pumping unit. The purpose of keeping the oil pumping unit balanced in different working states is achieved, manpower loss is saved, working efficiency is improved, and therefore the purposes that the oil pumping unit is not prone to sliding and equipment is prevented from tipping over when the oil pumping unit is kept balanced are achieved, universality of the equipment is improved, the purpose of fixing the heavy block is achieved, and the heavy block is prevented from sliding down and damaging the equipment.