Abstract: Organic phosphonate has thermal stability, good hydrolysis, good corrosion inhibition and scale inhibition performance, it is widely used in water treatment. Amino trimethylene phosphonic (ATMP) was synthesized by using formaldehyde, phosphorus trichloride and ammonium chloride as raw materials. The best synthetic process conditions were obtained by examining the corrosion inhibition and scale inhibition of each group of ATMP, as follows: holding temperature 110 ℃, holding time 3.5 h, materials ratio 3∶4∶1.2. The scale inhibition of ATMP is superior than its corrosion inhibition. So ATMP is generally used as scale inhibitor and to resist calcium carbonate and is used as the corrosion inhibitor alone rarely.