Abstract: In this study, chitin was extracted from Penaeus chinensis, and the protein was removed by protease and decalcified by citric acid.The protease activity was measured by Alcalase Alkaline protease. The optimal conditions of chitin preparation were determined by single factor experiment and Box-behnken response surface design. The optimal conditions of decalcification were obtained as follows: solid-liquid ratio 1 ∶ 12, reaction Time 2.5 h, citric acid concentration of 8%, ash content of 0.42%.The optimum conditions were as follows: adding 2200 U/g enzyme, reaction time 5 h, reaction temperature50 ℃, and the protein concentration could reach 31.42% by taking the protein content as the index. The experimental conditions are mild, rapid response, no environmental pollution, in line with the concept of pollution-free green, and to provide the basis for industrial production of chitin.