Abstract: The extraction conditions of chintin from residue of Portunus trituberculatus shell pretreated with neutral protease were optimized by single test,and the preparation conditions of chitosan from the chintin were optimized by orthogonal test.In extraction process of chintin,the optimal decalcifying conditions are as follows:temperature 30 ℃,HCl concentration 6% and soaking time with HCl solution 4 h,and the optimal deproteinizing conditions are as follows:temperature 90 ℃,NaOH concentration 6% and cooking time with NaOH solution 2 h.The optimal preparation condition of chitosan from the chintin are:temperature 90 ℃,NaOH concentration 50% and time 9 h.The extracted chitin and prepared chitosan meet the demands of food grade on quality index.

Key words: Portunus trituberculatus, shell, chitin, chitosan