Abstract: Objective:To optimize the flocculation process of dihydrogenchalcone in Lithocarpus polysachyus rehd using Box-Behnken design-response surface method. Methods:A new type of natural polymer flocculant“chitosan” was used to improve the purity of dihydrogenchalcone instead of the traditional flocculant“polyaluminium chloride”. The technological parameters were investigated in term of flocculant dosage, pH, flocculation time and temperature. Based on the single factor experiments, the optimal flocculation condition was obtained by using Box- Behnken design- response surface method and the mass fraction of dihydrogenchalcone“w” index. Results:The optimization result were:when the chitosan flocculant was used at0.54mL/g (dried leaves) (equal to 0.63g/L water extract) , the pH of the water extract was 6.17, the period of the flocculation was 73 min, the temperature of the water was 25℃, then the conment of dihydrogenchalcone could reach 12.53%. Conclusion:The flocculation effect of Chitosan was better than that of polyaluminium chloride, and the higher purity of dihydrogenchalcone was obtained with avoiding the use of aluminum ions.