A oilfield acidification corrosion inhibitor was synthesized by Mannich reaction of secondary amine, acetophenone and formaldehyde. The effect of the synthetic technology，including molar ratio of reactant, reaction temperature and reaction time, on the inhibition performance of the inhibitor was evaluated by coupon corrosion tests. In addition, the inhibition mechanism of the inhibitor was investigated by electrochemical test and scanning electronic microscope observation. The results showed that the inhibitor exhibited the best inhibition efficiency when the molar ratio of primary amine, acetophenone and formaldehyde was 1:2:5 and the reaction were maintained at 80℃ for 10 h. After compounded with polyether and propargyl alcohol, the inhibitor could reach the first-class level at the dosage of 0.5%. The corrosion inhibitor was assigned as a mixed inhibitor mainly which inhibited the anode process through electrochemistry method. The scanning electronic microscope observation indicated that the corrosion forms of steels were improved significantly after adding 0.5% corrosion inhibitor.