The activities of cellulase, alpha-amylase, and acid protease in ethanol + water at elevated CO2 pressure were investigated. The experimental results indicated that the operating conditions of under 30% (mass percent) ethanol concentration and lower than 35 degreesC were quite suitable for cellulase-ethanol-water systems using high-pressure CO2, but alpha-amylase treated with high-pressure CO2 was liable to denature. The results also showed that it was suitable to precipitate acid protease in high-pressure CO2 (upward 6.86 MPa) within a wide range of ethanol concentration (upward 50%) and temperature (under 60 degreesC).