A strain that has the ability to degrade cellulose was selected from the cold region and black glebe, and the morphological characteristics of the strain were observed and molecular biological identification was carried out. The response surface method was used to optimize the conditions for the degradation of corn stalk by this strain, and the structural changes and the main component changes of corn stalk before and after degradation were observed and determined. The results showed that the strain number was GS-4-21, and the ratio (D/d) of the transparent circle of the colony diameter was 5.54 ± 0.20. The enzyme activities of filter paper, exocellulase, endocellulase and β-glycosidase were 11.94±0.51, 12.07±0.43, 32.94±0.83 and 30.87±1.04 U/mL, respectively. The identified strain GS-4-21 belongs to the genus Streptomyces. When inoculated into the fermentation medium with pH 6 at a volume fraction of 3% and fermented at 28 ℃ and 160 r/min for 5 d, the degradation rate of corn stover reached 23.54%. SEM results show that the strain GS-4-21 had better cellulose degradation ability. The degradation rates of cellulose, hemicellulose and lignin in corn stover were 30.33%, 31.95% and 18.91%, respectively.