Lunan stone forest is a kind of typical karst in China, which is mainly developed underred soil. In the winter of 1999, three study sites were chosen in stone forest national park accordingto vegetation cover, geomorphologic location and soil types. CO2 concentration was measured withGastec pump at different depths of soil (20, 40, 60 cm) and at the same time soil samples weregathered and soil properties such as soil moisture, pH, soil organic content were analyzed and thetotal number of viable microbes were counted in laboratory. In the study, dependent variable waschosen as the mean soil log (PCO2), and soil properties were chosen as the independent variables.Multiple stepwise regression analysis showed that the total amount of microbes and soil moisture arethe best indicators of the CO2 production, with the equation LOG(PCO2) = - 0.039(TNM) - 0.056(Mo) + 1.215 accounting for 86% of the variation of the soil CO2 concentration, where TNM is thetotal number of microbes in the soil and Mo is the moisture of soil sample.