The invention discloses a cleaning tool for an insulator string. A plurality of fixed brushes are arranged on two fixed brush frameworks side by side; the frameworks are arranged on rotatable shafts; the rotatable shafts are arranged in a three-dimensional manner through spring connecting rods and screw rods to form an openable cuboid structure. When an insulator string needs to be cleaned, the two fixed brush frameworks arranged side by side are opened at the screw rods, a tool is arranged on the insulator string, each fixed brush is enabled to be between two insulators respectively, the screw rods are fixed through adjustable nuts, and two ropes are alternately pulled to achieve the purpose that the cleaning tool is utilized to clean all the insulators at the same time. The cleaning tool not only is simple to operate but also does not need to clean the insulators one by one with cleaning cloth, so that the cleaning efficiency is remarkably improved.