In order to investigate the effects of different groundwater depths on the yield and water use efficiency of summer maize under rainfed conditions, four treatments with groundwater depths of 0.7, 1.3, 1.8 m and the normal field depth (recorded as D0.7, D1.3, D1.8, and D2.4, respectively) were set up using the groundwater automatic control system. The soil moisture content, rainfall utilization rate, phreatic evaporation, plant height, leaf area index, yield and water consumption during the growth period of summer maize under rainfed conditions were analyzed. The results show that the groundwater depth has significant effects on the average soil water content, rainfall utilization rate, and water use efficiency under rainfed conditions. Compared with D2.4, the average soil moisture content during the whole growth period of summer maize under D0.7, D1.3, and D1.8 treatments increased significantly by 6.9%~28.6%, the rainfall utilization rate decreased by 23.2%, 11.4%, and 2.8%, respectively, and the plant height, leaf area index, and dry matter accumulation decreased by 1.7%~5.2%, 5.8%~13.7%, and 9.4%~19.5%, respectively. Compared with other groundwater depths, the D1.8 treatment can ensure the highest yield and water use efficiency of summer maize in this area.