The object of this study was to investigate characteristics of kiwifruit protesae and effect of this enzyme on the functionality of casein. The specific activity of crudely prepared kiwifruit protease on casein was 196.95 units/㎎ protein, it showed optimum activity at pH 3.0, 60℃. The degree of hydrolysis of casein with protease treatment steeply increased to 73.5% and 78.9% for 10 and 20 minutes and then reached 84.1% and 89.3% for 1 and 4 hours, respectively. Solubility of non heated control group was 0.2% at pH 4, while the sample groups treated with enzyme for 0, 10 and 20 minutes were 14.5%, 19.2% and 24.0%, respectively. Casein treated with protease showed marked increase in foam expansion near isoelectric point. However, enzymatically treated groups had lower foam expansion than the control groups. Foam stabilities of enzymatically modified groups were lower than those of the control groups at all pH. Emulsifying activity of the non-heated control group was 0% at pH 4, while the groups modified enzymatically for 0, 10, and 60 minutes showed 51.0%, 55.5% and 54.5%, respectively.