The dispersant is composed of natural polymers and synthetic polymers, which can disperse microcrystals of salts such as calcium carbonate and calcium sulfate, or silt in water to prevent sedimentation, thereby inhibiting the formation and deposition of calcium carbonate, calcium sulfate, and calcium phosphate scales. It also exhibits excellent dispersion performance for amorphous insoluble substances in water. This product is suitable for open recirculating cooling water systems in industries such as steel, chemical, and petroleum refining, and can be compounded with other water treatment agents such as polyphosphates, organic phosphonates, silicates, and molybdates.