Abstract: To explore the influence of exogenous microbial agents on microbial community and maturity effect during cotton straw composting, three treatments were designed with using cotton straw as raw material, and the composting process was carried out by inoculating liquid microbial agents and fermenting for 35 days. Inoculating 0.5% of the microbial agent T1 (Anoxybacillus rupiensis + Paenibacillus illinoisensis + Bacillus velezensis) and the microbial agent T2 (Anoxybacillus rupiensis + Paenibacillus illinoisensis + Bacillus velezensis + Geobacillus thermoleovorans), respectively, CK was the control group without microbial inoculation. Results show that inoculation microbial agents could accelerate temperature rise, promote the degradation of organic matter and nutrient retention, improve the compost maturity and seed germination rate, and significantly improve the degradation rate of cellulose, hemicellulose and lignin. Analysis of microbial community during composting showed that inoculation with microbial agent improved the diversity of microbial community, changed microbial community succession, and stimulated the potential functional bacterial taxa (Bacillus, Thermobifida, Ureibacillus and Saccharomonospora) and fungal group (Vishniacozyma, Unclassified_f_Dipodascaceae and Cladosporium), which were related to the degradation of organic matter. Redundancy analysis show that pH and TOC were the main driving factors of bacterial community change during composting, while environmental factors such as C/N played an important role in the formation of fungal community. Overall, inoculation with microbial agents could promote the composting process, improve microbial flora, reduce nutrient loss during composting and improve the quality of compost products, among them, the overall composting effect of microbial agent T1 was better.