Abstract: In order to clarify the effect of deficit irrigation on soil microbial communities during the growth period of sunflowers, field experiments were carried out in Hetao Irrigation District. The local irrigation level was taken as the control（330 mm, CK）, set mild water deficit（210 mm, W1） and severe water deficit（120 mm, W2）. The effects of deficit irrigation on soil microbial community and physicochemical properties in the surface layer（0-20 cm） at different growth stages of sunflower were analyzed, and the internal relationship between soil microbe and physicochemical properties was revealed. The results show that the treatment of W1 increases soil microbial diversity and the relative abundance of dominant phyla, such as Proteobacteria, Chloroflexi and Acidobacteria in bacteria, and Mortierellomycota in fungi. Compared with CK, the soil pH value decreases by an average of 0.13 units, temperature and nitrate nitrogen content increase by an average of 1.44 ℃ and 14.2%, respectively. Pearson correlation analysis shows that soil water content, temperature, pH, EC and nitrate nitrogen are the key factors affecting bacterial diversity. The temperature, ammonium nitrogen and nitrate nitrogen are the key factors affecting fungal diversity. Redundancy analysis shows that soil water content, EC and temperature are the main important factors affecting bacterial community structure. The soil water content, EC and ammonium nitrogen are the main important factors affecting fungal community structure. In summary, mild water deficit（W1） is the suitable water condition for microbial growth.