The multifunctional water treatment agent is developed. T he ex perimental results show that the agent has ex cellent properties in scale and corr osion inhibit ion. The inhibition r ate of CaCO3 is up to 90%, and corrosion rate is low er than 0. 1mm/ a. Fur thermore, t he agent also has ex cellent germicidal ability . The agent can be applied to smal-l scale circulating water system.