Abstract: The activities of cellulase in 10%-40% ethanol- water solution were investigated at temperatures of 20-40 ℃ and at pressures of 0.49-4.41 MPa. These data obtained are essential to purify cellulase by high pressure CO₂. The experimental results indicate that CO2 pressure is not the key factor of the loss of enzyme activities, but ethanol concentration and temperature markedly influence recovered activities. The optimum operating conditions are 30 % ethanol concentration solution and 35 ℃ for cellulase- ethanol- water systems using high pressure CO₂.