EDTMPA is nitrogenous organic polyphosphonic acid, a part of cathodic corrosion inhibitor. Its corrosion inhibition is 35 times better than that of inorganic polyphosphate. It is miscible with water, innocuous and none pollution to environment, has good chemical stability and temperature tolerance. It shows excellent scale inhibition ability under temperature 200C. It can dissociate into 8 positive-negative ions, thus can chelate with many metal ions to form polymer reticulation complex, to destroy the normal crystallization of calcium scale. EDTMPS shows better antiscale effects to calcium sulfate and barium.