0.3%时提高了21.1%。 Cross-linking of casein catalyzed by horseradish peroxidase was studied, which was demonstrated by SDS-PAGE analysis, spectroscopic analysis and capillary electrophoresis analysis. The cross-linking degree of casein was measured by capillary electrophoresis with an area normalization method. Response surface method was applied to optimize the reaction conditions for cross-linked casein. The optimal cross-linking conditions obtained were that enzyme addition level was 4.73μkat per gram protein, temperature was 37℃ and reaction time was 2.9h. Under these optimal conditions, the cross-linking degree of casein prepared was about 6.9%. Evaluation results show that emulsifying activity index of cross-linked casein at concentration of 0.01% has an increase of 8.7%, while emulsifying stability index of cross-linked casein at concentration of 0.03% has an increase of 21.1% comparing to that of native casein, which indicates the improvement in emulsifying properties of cross-linked casein.