Abstract: It is common practice to return field straw with urea to accelerate decomposition. To improve the microbial screening methodology and investigate the microbes responsible for decomposition of corn straw, nitrogen acclimatization of the microbial consortium GF-20 (GF-20) was performed. Compositional differences in the cultured microbial consortium and the microbe source were also evaluated. GF-20 was cultured until the 10^th generation in variable nitrogen conditionsammonium sulfate (N1), mixtures of ammonium sulfate and urea (N2-N5), and urea (N6). The corn straw decomposition ratio was determined to estimate the activity of the composite microbial system, and the composition diversity and function were analyzed by MiSeq high-throughput sequencing. The results showed that the N2 degradation rate was significantly higher than the other treatments. The bacterial source alpha diversity index (ADI) was significantly higher than the cultured microbial consortium, and the N2 ADI was significantly higher than the other nitrogen treatments. The bacterial composition also significantly differed between the source and consortium, as well as among the nitrogen treatments. The N2 treatment yielded the most diverse bacterial composition, with richer and more uniform flora structures and a higher carbohydrate metabolic pathway activity (which promotes corn straw degradation). Functional microbial strains involved in corn straw degradation were obtained after restrictive sub-generation of the microbial sources, which can accelerate corn straw degradation. The highest corn straw degradation efficiency of microbial consortium was observed with the 0.16% ammonium sulfate + 0.04% of urea nitrogen (N2) treatment. These findings provide a basis for developing microbial consortium used in commercial production decomposition.