Abstract: Long-term straw returning has a positive effect on improving soil fertility and maintaining high grain yield. Although there have been many studies on the responses of microbial community composition and diversity to straw returning, the relationship between the potential interactions, functionality at the community level and grain yield is still unclear. Based on the 28-year field experiment, this study selected no fertilizer (NF), chemical fertilizer (CF), and chemical fertilizer + straw returning (CFS) treatments to study the effects of long-term straw returning on the potential interactions and functionality of microbial communities and their contribution to grain yield. The results showed that compared with NF, maize yield increased by 58.72%~217.52% under the treatments of CF and CFS, but there was no significant differences between CF and CFS. Fertilization treatments significantly increased soil organic carbon and nutrient content, and the CFS showed more significant effects than CF. The analysis of the functional composition of the microbial community showed that the functional redundancy of the community level was the largest in CFS, and the relative abundance of chemical energy heterotrophic, lignin and cellulose decomposition groups was the highest. The results of the co-occurrence network showed that the potential interaction of microorganisms at the community level was the most in CFS (the highest community complexity). The results of random forest and structural equation model showed that community complexity had the greatest contribution to grain yield. In summary, long-term straw returning can not only significantly increase soil nutrient storage capacity, but also more stably maintain high grain yield by improving community level functionality and complexity on the basis of changing microbial community composition.