PBTCA·Na4 has low content of phosphoric, its structure contains both phosphonic acid and carboxylic acid group, which enables its good scale and corrosion inhibition properties. Its scale inhibition property under high temperature is far better than that of organophosph-ines. PBTCA·Na4 can improve the solubility of zinc salt, has good chlorine oxidation tolerance and good composite synergy. The solid state is easy deliquescence. PBTCA·Na4 is the widely used and high effective agent as composite scale and corrosion inhibitor, it is also the excellent stabilizer for zinc salt. PBTCA·Na4 is used as scale and corrosion inhibitor in circulating cool water system and oilfield refill water system, especially used together with zinc salt and copolymer. PBTCA·Na4 can be used in situations of high temperature, high hardness, high alkaline and high concentration index. PBTCA·Na4 is used as chelating agent and metal detergent in lavation fields.