<p>Given the shortage of pure water resources, treated wastewater irrigation (TWW) has been widely used in agriculture, which may significantly affect soil microbial communities that are vital to biogeochemical cycles. We conducted a laboratory experiment using TWW from domestic wastewater and pure water for irrigation, respectively. The comprehensive effects of irrigation water quantity and quality on the structure, diversity, and enzyme activity of farmland soil microbial communities were evaluated. Compared with pure water irrigation, the TWW irrigation treatment showed less reduction in sucrase activity at the end of cultivation and increased soil pH and TKN content. For the α diversity of soil microbial communities, it was not significantly altered by TWW irrigation. However, reducing the irrigation water quantity significantly altered the structure of the soil microbial community. With respect to microbial community and functional gene abundance, the reduction in irrigation water quantity had a more pronounced impact than TWW irrigation. Co-occurrence network analysis provided evidence that TWW might enhance the stability of soil microbial community structure. While this study generally suggests that TWW irrigation may have positive effects concerning the diversity and stability of farmland soil microbial communities, further investigation into the prolonged impacts of TWW irrigation is still necessary.</p>