Abstract: To resolve the problem of soil nutrient and water deficiency in arid and semiarid regions of Northwest China, and considering the symbiotic relationship between microbes and crops, we set up two water regimes: drought stress (35% of the soil water holding capacity) and normal water supply (75% of the soil water holding capacity), two film mulching patterns (non-film mulching and film mulching), and four levels of microbial inoculation [single inoculation with AM fungi (AM), single inoculation with phosphate solubilizing bacteria (PSB), co-inoculation of AM fungi with phosphate solubilizing bacteria (AM+PSB) and the control (CK)]. This study aimed to evaluate the effects of microbial inoculation on maize growth, nutrient absorption, and water use efficiency under different treatments of water regime and film mulching. Results showed that drought stress significantly increased the mycorrhizal colonization of inoculated plants, but significantly decreased soil external hyphal length, T-GRSP and EE-GRSP content. Under drought stress, AM inoculation showed the best promoting and mycorrhizal effect on maize growth by increasing biomass and water use efficiency, soil organic carbon content, the absorption and transportation of soil N, P, K, and thus increasing the N, P, K uptake. Under normal water supply, the inoculation effect of AM+PSB was better than that of AM or PSB treatment, especially combined with film mulching. Results from correlation analysis showed that plant biomass, leaf SPAD value, and nutrient uptake of maize aboveground were significantly positively correlated with soil external hyphal length, whereas water use efficiency was significantly negatively correlated with soil external hyphal length.