Abstract: Using ethanol as the solvent, flavonoids was extracted from the corn cob by oscillation method. Based on results of single factor experiments, using Box-Behnken central composite design, four factors three levels experiment was designed. Results were analyzed by response surface methodology with Design-Expert, and the extraction of flavonoids from corn cob was set up. The regression equation was reasonable and reliable by checking. Extraction conditions of flavonoids from the corn cob were optimized. The result showed that the main factor of influencing flavonoids extraction was ethanol concentration, next was particle size, temperature and the ratio of material to liquid was less effected. These optimum extracting conditions were 85% ethanol concentration, 80 particle size, and 1∶25 ratio of material to liquid, temperature 51℃, extraction 2h, the yield of flavonoids was 0.289%. The actual measured value and the theoretical value (0.294%) of the difference was smaller, the relative error was 1.72%. The reliability of the model was proved fully.