Long-term continuous two-crop winter wheat and summer corn rotation with no-tillage,direct drilling and conventional tillage affected the structure and numbers of the microbial flora for nitrogen transferous bacteria in soils.In the layers of 0~0.1m and 0.1~0.2m soils,the numbers of anaerobic dinitrogen fixed bacteria in no-tillage were increased remarkably,and aerobic dinitrogen fixed bacteria in no-tillage and conventional tillage were also increased compared to other tillage treatment.The numbers of denitrifying bacteria were decreased and differed insignificantly in the surface soil layer for the three tillage methods,but conventional tillage had more and direct drilling less denitrifying bacterial numbers in the 0.1~0.2m and 0.2~0.3m soil layer.Ammonia oxidizing bacteria fluctuated largely,and no-tillage soil had more numbers.Nitrite oxidizing bacteria were increased in no-tillage soils in 0~0.1m soil layer,but in 0.1~0.2m soil layer it were more in no-tillage and conventional tillage soils.