A highly active cellulose-decomposing strain XWS-12 was isolated from the soil of wheat and maize straw returning by enrichment culture and Congo red staining test. The isolated strain was identified by phylogenetic relationships based on 16S rRNA gene sequences, and this strain was preliminarily identified as Burkholderia sp. XWS-12. Using corn straw and bran as carbon source, the cellulase producing conditions of the bacterium were analyzed by single factor experiments, including nitrogen source, incubating time, initial temperature, initial pH et al. The results showed that the optimal cellulase producing conditions of Burkholderia sp. XWS-12 were as follows: the best nitrogen source was NaNO3, incubating time was 60 h, initial temperature was 37℃ and initial pH of culture medium was 4, under which the activities of the CMCase activity reached 25 U/ml. The optimal reaction temperature of the crude enzyme solution was 50℃, the optimum reaction pH value 5. In the range of pH 4–8, the enzyme activity was more stable. In different temperature conditions, the results of the enzyme activity change showed that when the temperature was more than 50℃, the enzyme activity decreased significantly. Under the temperature of 50℃ for 1 h, the loss of enzyme activity was above 53%.