The invention provides a scaling inhibitor applied to industry cooling water systems. The scaling inhibitor is an aqueous solution of flake-like graphene oxide, the concentration of the scaling inhibitor ranges from 0.001 to 10g/L, and particle size ranges from 15 to 800nm. The invention also provides a preparation method of the scaling inhibitor; according to the preparation method, flake-like graphene oxide scaling inhibitor is added in cooling water, and the flake-like graphene oxide aqueous solution is obtained via magnetic stirring and ultrasonic dispersion. According to applications, the flake-like graphene oxide scaling inhibitor is added into industrial recycling cooling water, when the concentration of scale-forming ions in cooling water is relatively large, and scaling is caused, the surfaces of scale-forming particles (such as calcium carbonate) are coated by graphene oxide, the crystal type of scale-forming substances, such as calcium carbonate, is changed, and flocculent mild scale is formed, so that adhesion of the scale-forming substances, such as calcium carbonate, in water onto the metal surfaces of heat exchange equipment is not easily caused, the flocculent mild scale is removed via drainaging of the cooling water systems, and scaling inhibition is achieved.