Abstract: Fourteen corrosion inhibitors of phosphonic acids were synthesized of which seven are new compound. The influences of concentrations of phosphonic acid and pH of solutions on corrosion inhibiting properties were investigated through weight-loss tests, the relation between structures and corrosion inhibiting properties were analyzed, and the corrosion inhibiting mechanism was discussed. The results showed that corrosion inhibiting ability of the solution were strengthened with increase of phosphonic acid concentration in the concentration less than 100 mg/L or in high pH value solutions.Analysis on the surface configuration and surface film component of Q235 steel manifested that phosphonic acid was an adsorbing type corrosion inhibitor and the giving electron group in benzene ring was in favor of forming compact surface film.