Abstract: N-dodecyl-di(methylenephosphonic acid) was prepared by Mannich reaction,with dodecylamine,formaldehyde and phosphorous acid as starting materials and hydrochloric acid as catalyst.The yield reaches 95.75%.The targeted product sodium N-dodecyl-di(methylenephosphonate) was prepared by reaction of NaOH with the N-dodecyl-di(methylphosphonic acid).Chemical structure of the product was characterized by ³¹PNMR,¹HNMR and element analysis.Results showed that the product fits the requirement with rather high purity.Surface tension of solution of the product was determined.Results showed that the surface tension data changes with the pH regularly,and trend of the changes are consistent with structure information of the product.

Key words: sodium N-dodecyl-di(methylenephosphonate), Mannich reaction, characterization, surface tension