N-alkyl-2-(4-hydroxybut-2-ynyl) pyridinium bromides (designated as O-16) were synthesized and characterized by 1H NMR、13C NMR and MS. The inhibitive performance of O-16 on X70 steel in 20% HCl was evaluated by weight loss，Tafel polarization and EIS techniques. The results showed that O-16 exhibited good inhibitive performance against acid corrosion for X70 steel. The inhibition efficiency increased with increasing concentration and could reach 99% at 3?0-5M of O-16. Tafel polarization curves of X70 steel indicated that O-16 is a mixed-type inhibitor controled predominantly cathodic reaction. The corrosion products formed on X70 steel surface were observed by SEM.