In order to investigate the effects of different irrigation and fertilization on soil microbial properties of summer maize field, we used ZN99 with high nitrogen use efficiency as the test material. The experiment adopted the split plot design which included two irrigation levels (526 mm and 263 mm) as the main plots, three fertilizer types (U, M, UM) and two fertilizer levels (N 100 kg . hm-2 and 200 kg . hm-2) as the subplots. The results showed that the irrigation level affected the regulating effects of fertilizer on soil microbial biomass (carbon and nitrogen) and microbial di- versity. The organic fertilizer application must be under the sufficient irrigation level to increase the soil MBC (14.3%-33.6%), MBN (1.8-2.3 times) and abundance significantly. A moderate rate of irrigation, higher rates of organic fertilizer application or organic manure combined with inorganic fertilizer could increase the nitrogen-fixation species and quantity of Firmicutes, γ-Proteobacteria and α-Proteobacteria in the soil. Under the same N level, there was no significant difference of grain yield between organic manure and inorganic fertilizer treatments. Considering sustainable production, proper organic manure application with moderate irrigation could increase the quantity of the soil microbial biomass and microbial diversity, and improve the capacity of soil to supply water and nutrients.