The invention provides an upper support roll balancing device of a rolling mill. The upper support roll balancing device comprises a carrying pole beam and a balancing cylinder, wherein the carrying pole beam is positioned above an upper cross beam of the rolling mill; the balancing cylinder refers to two differential hydraulic cylinders arranged at the two sides of the center line of the upper cross beam of the rolling mill; and each differential hydraulic cylinder comprises a cylinder body and a cylinder rod matched with the cylinder body, wherein the cylinder bodies are connected to the upper cross beam of the rolling mill, the cylinder rods are connected to the carrying pole beam, and convex-concave combination structures are arranged between each cylinder rod of differential hydraulic cylinder and rodless cavity bottom. By adopting the upper support roll balancing device provided by the invention, the damage of a sealing element caused by the vibration of the rolling mill can be effectively avoided, and the equipment maintenance frequency and time are reduced; meanwhile, the impact on the equipment is also reduced when the hydraulic cylinders reach the travel limit; and the equipment piping and overhauling operations are more convenient and safer.