To investigate the effects of returning granulated corn stover on biological properties and bacterial communities of black soils, a 2-year field experiment was conducted in Jalaid Banner, Inner Mongolia in 2016 and 2017. Amount of corn stover incorporated in soil were 0 kg/hm² (CK, 0%), 4500 kg/hm² (JG1), 5250 kg/hm² (JG2), 6000 kg/hm² (JG3), 6750 kg/hm² (JG4), and 7500 kg/hm² (JG5, 100%). The changes in soil sucrase, urease, catalase, alkaline phosphatase enzyme, microbial biomass carbon, and nitrogen, as well as the bacterial community were studied. Results showed that, returning corn stover to the field increased the activity of soil sucrase (by 3.29%-32.12%), urease (by 5.32%-52.66%), catalase (by 0.60%-27.11%), alkaline phosphatase enzyme (by 10.89%-64.20%), microbial biomass carbon (by 1.32%-7.07%), and nitrogen (by 16.35%-80.46%). The returning of corn stover increased the relative abundance of Proteobacteria and Firmicutes in black soil, which can enhance the ability of soil nitrogen fixation and disease resistance and reduce the probability of soil disease through decreased relative abundance of Actinomycetes. New bacteria with the capability for nitrogen fixation, phosphorus uptake, and soil improvements also increased. In conclusion, returning of corn stover to soil has important ecological impacts on the agroecosystem, which can enhance the abundance and generic diversity of soil nematodes, creating a stable and healthy soil ecosystem. According to our study, 6750 kg/hm² or 90% returning rate is suitable for granulated stover returning.