A phosphorus-free corrosion and scale inhibitor used in circulating cooling water of central air conditioning is provided, which contains tourmaline, green corrosion and scale inhibitor, zinc salt and the like, wherein the content of the tourmaline is 5-500 g/t (calculated based on solid form); the content of the green corrosion and scale inhibitor is 5-50 g/t (calculated based on liquid form); and the content of the zinc salt is 0.2-0.8 g/t (calculated based on solid form), wherein the tourmaline includes dravite, schorlite, elbaite, manganese tourmaline, uvite or the like. The green corrosion and scale inhibitor contains any one, or two or three of polyaspartic acid, polyepoxysuccinic acid and polymaleic acid. Copper corrosion can be effectively inhibited by adding 0.2-2 g/t of benzotriazole (calculated based on solid form) into copper-containing devices. Also disclosed is a method of preparing the phosphorous-free corrosion and scale inhibitor used in circulating cooling water of central air conditioning.