<p>Salinity stress and waterlogging-induced hypoxia in plant roots affect soil nutrient turnover and enzymatic activities, which impacts crop productivity. Aerated drip irrigation (ADI) is an effective approach to reduce salinity and waterlogging stresses in plants, but the influence of aeration frequency on the root-zone microenvironment under combined stress is still unclear. This study investigated the changes in rhizosphere soil properties, bacterial community characteristics, and plant growth performance of lettuce under individual and combined stresses of salinity and waterlogging with different aeration levels and frequencies. Results showed that the root length of stressed plants decreased by 24.3–68.5%, with 37.9–67.2% reduction in the aboveground fresh weight. The combined stress exhibited greater effects on root growth and plant biomass than individual stresses. ADI with a dissolved oxygen concentration of 15&#xa0;mg/L increased soil bacterial diversity and the proportion of aerobic bacteria. Compared with non-aerated irrigation, ADI resulted in greater root surface area (by 7.2–7.6%) and root volume (by 31.8–45.9%) under stress conditions. A higher aeration frequency (every 1&#xa0;day) increased soil NH₄⁺-N content (by 18.9%), sucrase activity (by 73.8%), and plant fresh weight (by 73.8%). Mantel’s tests revealed strong correlations between soil bacterial community structure and key environmental factors—including NH₄⁺-N, NO₃^⁻-N, and sucrase activity. This study indicated that ADI (particularly at a higher aeration frequency) improved the root-zone microenvironment of lettuce by increasing soil nutrient levels, modifying bacterial community structure, and stimulating enzymatic activities. This microenvironmental improvement promoted plant nutrient uptake and utilization, root growth, and stress resistance under saline and waterlogged conditions, consequently increasing crop yield.</p>