Eucalyptus' leaves were studied as the main raw material. The continuous phase transition extraction progress for eucalyptus' polyphenols was optimized by single factor test and Box-behnken. The effects were discussed for extraction time, extraction temperature and extraction solvent percentage on the yield of polyphenols. The optimal extraction conditions were found as follows: extraction temperature 79.99 ℃, extraction time 119.98 min and solvent concentration 78.13%. Under the optimal conditions, the yield of polyphenols was 11.58 g/100 g. The actual polyphenols yield was 12.01 g/100 g with the relative error 3.65%. The extraction conditions parameter obtained by the Response Surface Methodology to optimize the extraction technology was credible and own application value.