Abstract: Six different imidazoline quaternary ammonium salts were synthesized with the use of valeric acid,decanoic acid,oleic acid,diethylenetriamine,benzyl chloride and thiourea as raw materials.The corrosion inhibition performances of quaternary ammonium salts of thioureido alkyl imidazoline and alkyl imidazoline on carbon steel in 1.0 mol/L HCl medium were compared at 80℃ via both static mass loss and polarization curve methods.The synergies between each of these two corrosion inhibitors and each of the inorganic anions or anionic surfactants were also investigated.The results show that the inhibition effect of quaternary ammonium salt of thioureido alkyl imidazoline reaches a 98.3% rate of corrosion inhibition and is significantly superior to that of quaternary ammonium salt of alkyl imidazoline.The best corrosion inhibition effect is achieved when the mass ratio of quaternary ammonium salt of thioureido alkyl imidazoline to I^- is 1:1 during preparation process.This gives a corrosion inhibition effect 1.5% higher than that of quaternary ammonium salt of thioureido alkyl imidazoline compounds used alone.