The invention relates to the field of microorganisms, belongs to agricultural intensification production technologies, and particularly relates to a complex microbial inoculant for degrading straw cellulose. Active components of the microbial inoculant comprise, in weight percent, 60% of Bacillus cellulosilyticus and 40% of beta-glucosidase production Bacillus megaterium, wherein the CGMCC (ChinaGeneral Microbiological Culture Collection Center) NO. of the Bacillus cellulosilyticus is 1.15312, and the CGMCC NO. of the beta-glucosidase production Bacillus megaterium is 1.9072. The enzyme production activity of the complex microbial inoculant has no significant difference at the temperature of 10 DEG C, the complex microbial inoculant has high stability, cellulose degradation rate is 67.53%, hemicellulose degradation rate is 61.81%, and the complex microbial inoculant is applicable to northeast cold weather.