Abstract： According to the principle of ionic switch, the deacidification process of vacuum gas oil was studied by using ethanolamine ethanol solution. The process conditions and reaction kinetics were obtained. It was showed that under the conditions of ratio of deacidification agent to oil at 4:15, reaction temperature 60℃ and reaction time 50 min, the deacidification rate of vacuum gas oil could reach more than 70%. After the deacidification, the treated oil quality was significantly increased, the acid value of naphthenic acid obtained from the treated oil was 157 mg KOH/g. The conditions of deacidification process were mild without emulsification phenomenon, waste water and residue, and the deacidification agent could be reused, which shows a good economy.