Abstract: Preparation and enzymatic properties of alkaline protease immobilized with sodium alginate were studied.Based on single factor experiments, response surface optimization method was used to determine the optimal conditions for immobilization.The results showed that optimum conditions were:concentration of sodium alginate 3.1%, concentration of CaCl 2 3.0%, pH 9.4, amount of free enzyme 10000U/g, time 1.8h, enzyme activity up to 5518U/g.The optimum pH was 10, optimum temperature was 60℃, the thermal stability and operational stability of the immobilized enzyme was better.Furthermore, the enzyme activity of immobilized enzyme was only reduced by 40%after used five cycles.