Abstract: This article aims to screen an efficient cellulolytic mixed strain from the soil and rotten stalk, and study its application to natural cellulose. Congo red stain was used to primarily screen the isolated strains, and DNS method was used to measure all strains’CMC enzyme activity. A complex microbial system capable of degrading cellulose with high efficiency was constructed by mixed cultured of strains of high enzyme activity and no antagonism. The results showed that, the enzyme activity of 3 fungus mixed culture was higher than that from the fermentation of single fungus. Strain F1 was identified as Botryosphaeria, F2 was identified as Rhizopus oryzae and F5 was identified as Fusarium oxysporum by morphological and molecular technology. When the carbon source was straw, the CMC enzyme activity of F1, F2, F5 was 39.2 μmol/mL, 31.4 μmol/mL, 40.6 μmol/mL respectively. The cellulase produced by mixed fermentation of F1 F2 F5 showed a strong enzyme activity of 50.12 μmol/mL. The enzyme activity of fungus community was 23% higher than that of F5 single fungus. The experiment results indicated that the enzyme activity of the microbial community was higher than that from the fermentation of single fungus, and fungus F1, F2 and F5 had tremendous potential value for microbial fertilizer.