A cooling water recycling filter comprises a supersonic and electromagnetic wave limescale processor installed inside a main water recycling system of water storage tank and a sub water recycling system installed outside a main water recycling system. The sub water recycling system comprises a water quality control unit, a limescale processor unit, a limescale separation and filter unit and a high level oxidization and processing unit. An electric conductivity sensor, a PH value sensor, and an ORP oxidization and reduction potential meter of water quality control unit are used to measure the values of water quality. A limescale processor and impurities separator is used to filter impurities of the cooling water. After the cooling water is filtered precisely by the limescale separation and filter unit, the cooling water is sterilized by a copper and silver sterilizing and algae-killing unit of a sterilization unit.