Straw returning is an important measure to improve soil fertility. Aiming at the problems of soil degradation，such as thinning of cultivated layer and secondary salinization of soil，in the spring corn area in the transition zone from the Inner Mongolia Plateau to the Songliao Plain，under the condition of long-term continuous cropping of corn，used the method of field positioning test to study the effects on soil microorganisms under the condition of returning straw with rotary tillage to the field for different consecutive years(8，5，2 years). The results showed that Proteobacteria was the most abundant bacteria in straw returning soil，followed by Actinobacteria，Gemmatimonadetes and Bacteroidetes. The types of fungi were Ascomycota and Basidiomycota. With the increase of straw returning years，the relative abundance of Proteobacteria and Acidobacteria were increased，the relative abundance of Actinobacteria was decreased，while the relative abundance of Bacteroidetes was relatively stable. The relative abundance of Ascomycota，Basidiomycota and Zygomycota were decreased first and then increased，while the relative abundance of Glomeromycota and Chytridiomycota was opposite. At the genus level，the relative abundance of Sphingomonas，Lysobacter and Hannaella were increased first and then decreased，while the relative abundance of Leptocephalia and Monodictys had opposite changes. The relative abundance of Pseudomonas and Fusarium were decreased，and the relative abundance of Gaiella was relatively stable. The relative abundance of Guehomyces was increased. The inflection point of relative abundance of bacteria and fungi occurred 5 years after straw returning. With the increase of straw returning years，the diversity of soil bacteria and fungi were decreased. The difference species of soil between straw returning and straw not returning are Aquicella，Fusicolla and Spizellomyces. It can be speculated that straw returning can increase the content of soil nitrogen and potassium，and reduce the disease. The soil microbial composition was changed after corn straw returning for many years，and the soil microbial diversity decreased after corn straw returning for 5 years.