[Objective] Addressing the spatiotemporal imbalance of water supply and demand and the insufficient system resilience in the receiving area of the Middle Route of the South-to-North Water Diversion Project (SNWDP-MR), this study aims to quantify the regulation benefits of online regulation projects and extract their multi-scenario adaptive scheduling modes. [Methods] By integrating 23 controlling reservoirs along the route, a multi-objective water resource optimization allocation model was constructed. Based on long-series hydrological data from 2010 to 2023, water allocation schemes for the planning horizon years of 2025, 2030, and 2035 were simulated and comparatively analyzed under scenarios with and without online regulation projects. [Results] Online regulation projects significantly enhance water supply security and stability while optimizing the water supply structure. Specifically, the average water shortage rates in the receiving area for the respective planning years decreased from 8.47%, 6.36%, and 6.29% to 7.28%, 5.13%, and 5.13%. The coefficient of variation (C_v) of the water shortage rate decreased by 5.50%, 7.09%, and 14.94%, respectively, indicating a significant attenuation in supply volatility. Furthermore, the proportion of groundwater supply decreased by 0.48%, 0.67%, and 1.61%, respectively. [Conclusion] Through optimized scheduling strategies of “storing during wet periods, supplementing during dry periods, and regulating during normal periods”, online regulation projects effectively alleviate spatiotemporal supply-demand imbalances and bolster the resilience of the water supply system against extreme hydrological events. These findings provide a scientific basis and technical support for the future planning of the SNWDP-MR and the construction of regional water networks.