EDTMPS is nitrogenous organic polyphosphonic acid, a part of cathodic corrosion inhibitor.Its corrosion inhibition is 3~5 times better than that of inorganic polyphosphate. It can be fully dissolved in water, innocuous and none pollution to environment, has good chemical stability and thermal tolerance. It shows excellent scale inhibition ability under temperature 200¡æ. 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 sulfate.