Abstract: Environmental conditions such as low temperature and dry climate in the northern alpine region will make the in-situ degradation of cellulose substances such as straw, cattle and sheep manure slow, resulting in difficult cultivation and low seeding quality in the next year. In order to improve the degradation efficiency of cellulose substances in the northern alpine region, the soil at mining area in the alpine grassland area and the microbial agent with good cellulose degrading ability were selected as the bacterial source materials through the laboratory culture experiments. Cellulose substances in corn straw were taken as the degradation objects. Enrichment culture and temperature gradient acclimation methods were used to select the complex bacteria that were resistant to low temperature (15 ℃) and efficient in degrading cellulose. The degradation characteristics of cellulose substances and the diversity of complex bacteria composition were determined. The results show that, the cellulose degradation rates of SL₁₅ (the bacteria source is the soil of mining area), MM₁₅ (the bacterial source is cellulose degrading bacterial agent) and MS₁₅ (the bacteria source is the soil of mining area with added cellulose degrading bacteria agent) were 22.33%, 26.33%, and 29.23%, respectively, when cultured at 15 ℃ for 15 days. The composite strain MS₁₅, which was selected by adding exogenous cellulose degrading bacteria from indigenous microorganisms, had the strongest cellulose degrading ability, and the highest filter paper enzyme activity and endonuclease activity, which were 4.6925 U/mL and 2.2267 U/mL, respectively. High-throughput sequencing revealed that Proteobacteria, Bacteroidetes, Firmicutes, Ascomycetes and Basidiomycetes were the dominant phyla in all complex bacteria. Sphingobacterium, Chryseobacterium, and Brucella all promoted the degradation of cellulose. Sphingobacterium and Basidiomycota were the dominant bacteria in MS₁₅, which significantly enhanced the activity of cellulose degrading enzymes and the degradation rate of cellulose substances. The study showed that during the screening process, the low-temperature resistant cellulose degrading bacteria were enriched and irrelevant bacteria were eliminated. The addition of exogenous cellulose degrading bacteria into the indigenous microbial community enhanced the microbial activity and significantly improved the degradation rate of cellulose substances. It can provide technical support for further developing cellulose-degrading complex bacteria and promote in situ return of cellulosic substances such as corn straw to field at low temperature.