The behavior of oxidative viscosity reduction using microemulsion catalyst was investigated according to the heavy oil recovery technology of oxidizing reduction. FeB is selected from11 kinds of synthetic oil-soluble catalyst，by which a microemulsion catalyst system can be made（mass ratio of catalyst FeB∶distillate oil∶water∶emulsifier is 1.5∶40∶57.3∶1.2）with better dispersion in the heavy oil. The performance evaluation results show that under the experimental condition（the mass ratio of micoroemusion catalyst and heavy oil is 0.2%，and mass ratio of oil and water is 2∶3，and volume ra? tio of air and heavy oil is 40∶1，and the oxidation temperature is 200 ℃and reaction time is 120 h），the viscosity of heavy oil in Liaohe oilfield and Suizhong 36-1 oilfield dropped from 8 088 and 2 004 mPa?s to 683 and 267 mPa?s respectively，and the effect of viscosity reduction is obvious. Microemulsion catalysts used in the heavy oil mining technology of oxidative viscosity reducing will help to promote the efficiency of the heavy oil development and the research and application of new EOR technology.