To explore the effects of conservation tillage on soil productivity, a field experiment with the five treatments of no-tillage with 20 cm(NS₂₀) and 40 cm(NS₄₀) standing stubble, no-tillage with 20 cm(NPS₂₀) and 40 cm(NPS₄₀) pressed stubble and conventional tillage, and conventional tillage(CT) were carried out to study the changes of soil organic matter(SOM), soil microbial biomass carbon(MBC), soil microbial biomass nitrogen(MBN), crop yield and water use efficiency(WUE) in the Heihe River Basin. Results showed that SOM, MBC and MBN in 0-20 cm soil layer under conservation tillage, which decreased with increasing soil depth under conservation tillage, were higher than that under CT. MBN significantly accumulated in surface soil under conservation tillage. Correlation analysis showed that MBC was remarkably correlated to SOM(r=0.85 and p<0.05), while there were no significant correlation between MBN and SOM(r=0.47 and p>0.05). Conservation tillage improved grain yield and WUE compared to CT. NPS₂₀ and NPS₄₀ had the best yield effects, increasing grain yield by 53.08% and 46.59% compared to CT, respectively. WUEs in NPS₂₀, NS₄₀, NPS₄₀ and NS₂₀ were increased by 58.02%, 43.40%, 47.27% and 23.78%, respectively.