Abstract: In order to further improve the cellulose degradation efficiency of composting materials and shorten the composting time, in this study, the pre-mixed cellulose-degrading microbial agent M (M) was inoculated into the mixture of sheep manure and straw, then an aerobic composted fermentation was performed and the effect of the microbial agent M on sheep manure composting was analyzed. The results showed that compared with CK group, after inoculation of M, the temperature rise time (>50 ℃) was shortened by one day, the high temperature stage was extended by 2 days, and the composting period was shortened by 4 days. At the end of composting (25 d), the carbon nitrogen ratio of the M group (12.77) was significantly lower than that of the CK group (16.44) (p<0.05), while the seed germination index (98.20%), total nitrogen (23.37 g·kg⁻¹), available phosphorus (13.13 g·kg⁻¹), available potassium (51.12 g·kg⁻¹), cellulose degradation rate (28.33%) and hemicellulose degradation rate (38.32%) were significantly higher than those of CK group (p<0.05). The total nutrients content (8.76%) can meet the national standard of organic manure (≥5%). The results of cellulase activity determination showed that during the whole composting process, the activities of filter paper enzyme (FPase), carboxymethyl cellulase (CMCase) and β-glucosidase (β-Gase) of M group were all significantly higher than those of CK group (p<0.05). The cellulase activities of M group reached the highest during the high temperature fermentation stage of composting (4−8 days), which were 57.80 U·mL⁻¹, 10.41 U·mL⁻¹ and 75.77 U·mL⁻¹, respectively. In addition, after inoculation with MR, which is a mixture of M and a commercial decompostion microbial agent R (R), the indexes of fermentation compost were all better than those of M and R groups. Except cellulose degradation rate, there was no significant differences in other indexes between M group and R group (p>0.05). In this study, the composite microbial agent M was inoculated for composting fermentation of sheep manure, which could significantly reduce the content of cellulose and hemicellulose, improve the nutrition of composting, shorten the composting time, and the fermented organic manure could be used for agricultural production.