The top circulation reflux system of atmospheric and vacuum towers, catalytic towers and coking towers suffer from the phenomenon of pipe wall thinning and leakage as well as salt formation in the pump body over the past few decades. This can be attributed to the increased processing volume of high acid crude oil. The most severe corrosion among them threatens the long-term safe operation of the units, particularly the top cycle of the catalytic fractionation tower. Herein this study synthesised a corrosion inhibitor that is appropriate for processing high-acid crude oil in the fractionation tower's top cycle, primarily to prevent catalytic corrosion. In addition, the electrochemical measurement and the weight loss method were employed to evaluate the corrosion inhibition of the water-soluble and oil-soluble imidazoline inhibitors, respectively. The results indicated that corrosion inhibition of water-soluble imidazoline was WCI≈WBI>WAI. Based on assessment results in the simulated oil-running environment of the HCl-water system and the HCl-H2S water system, the synthesised oil-soluble inhibitor (OBI> OCI> OAI) has a better overall corrosion inhibition than the water-soluble inhibitor. The most effective corrosion inhibition on the catalytic top running oil are demonstrated by OBI, an oil-soluble corrosion inhibitor that is synthesised on-site.