To explore the effects of straw returning on soil microbial diversity and community composition in different depths of soil layers，the effects of straw return on soil microbial population，enzyme activity，bacterial and fungal diversity，and community structure in 0-10，10-20，and 20-30 cm soil layers during the wheat harvest period were studied using cultivable methods，kit enzyme activity determination methods，and high-throughput sequencing techniques. The results showed that long-term straw returning increased soil enzyme activity and the number of cultivated microorganisms in all three soil layers. The activities of soil urease，catalase，sucrase，alkaline phosphatase，cellulase，as well as the number of bacteria，fungi，ammonifying bacteria，nitrobacteria，and cellulose degrading bacteria in 0-10 cm soil layers showed significant differences compared to the control(P<0.05). Moreover，the soil enzyme activity and microbial quantity effect of returning straw to the field decreased with the increase of soil depth. Long term straw returning significantly increased the α diversity index(P<0.05)of bacterial，namely ACE index，Chao1 index，Shannon index，etc. in the 10-20 cm soil layer，changed the β diversity of bacteria and fungi in each soil layer. In addition，long-term straw returning also changed the community structure of bacteria and fungi，and had a significant impact on the bacterial community structure. In the 0-10 cm soil layer，Acidobacteria，Proteobacteria，Planctomycotes，and Latescibacteria all significantly increased(P<0.05). As the soil depth deepened，the differences in bacterial community structure became smaller and smaller. In addition，returning straw to the field could make the interaction and connection between bacterial communities closer，but it reduced the stability of fungal communities. Long term straw returning to the field had a significant positive effect on soil enzyme activity，cultivable microbial quantity，bacterial community structure and diversity，and had a greater positive impact on bacteria in the soil. This study clarified the soil microecological effects of straw returning to the field，providing theoretical support for scientific straw returning to the field.