Objective To explore the effects of SO2 4- and PO3 4- on the performance of mannich base hydrochloric acid corrosion inhibitor. Methods Using static weight-loss method, polarization curve, scanning electron microscope and energy spectrum analysis, the effects of SO2 4- and PO3 4- on the performance of mannich base hydrochloric acid corrosion inhibitor were studied and its mechanism was explored. Results In corrosion medium with 10% HCl and 0. 1% mannich base, with the increase of SO2 4- mass fraction, the corrosion current density increased from 2. 81 μA / cm2 to 7. 32 μA / cm2 , the corrosion rate significantly increased and the corrosion inhibition effect was weakened; on the contrary, with the increase of PO3 4- mass fraction, the corrosion current density decreased from 2. 81 μA / cm2 to 2. 41 μA / cm2 , the corrosion rate decreased and the corrosion inhibition effect was strengthened. Conclusion SO2-4 penetrated into the steel surface adsorption film through the holes and defects, forming cracks in the film, leading to erosion and damage of the adsorption film, and the effect of mannich acid hydrochloric acid corrosion inhibitor was suppressed. The corrosion products of PO3 4-and Fe3+ formed a layer of dense membrane on the steel surface, making the adsorption film formed by the corrosion inhibitor more dense, leading to difficulty in the contact of corrosive medium and metal surface, meanwhile, the diffusion resistance of ions or dissolved oxygen was increased, and the performance of mannich base hydrochloric acid corrosion inhibitor was promoted.