Objective To evaluate the catalytic esterification performance of proteases in micro-aqueous systems and to study the suitable conditions for maintaining protease activity. Results It was found that the protease showed better enzyme catalytic activity in the micro-aqueous phase containing 4% boric acid-borax buffer than that of the pure organic phase. The protease activity was easily activated by 0.20 M boric acid-borax buffer, and the enzyme activity was still high for a long time in alkaline environment (pH 8.40-9.60) and under the temperature of 40-55 degrees C. Experiments using protease and Candida lipase to synthesize sucrose-6-ethyl ester showed that protease had better esterification activity thanCandidalipase in the micro-aqueous phase.