The influence of compression and decompression rates of carbon dioxide on the physiology of Absidia coerulea and Saccharomyces cerevisiae was investigated. Besides parameters such as pressure, temperature, exposure time, water content, and initial pH, the influence of either compression or decompression rate on the biological behavior of microorganisms was quite essential. For both microorganisms studied, an optimal rate for either compression or decompression process exists due to the integrated effect of pressure, exposure time as well as compression or decompression speed. The decompression rate has no significant effect on cell's viability after 180 min exposure in compressed CO2 because almost all the microorganisms were died before decompression.