[Objective] Against the backdrop of escalating flash flood risks in mountainous rural areas due to climate change and the inadequacy of conventional urban-centric assessment frameworks for the "natural-social" coupled disaster mechanism in the countryside, this study aims to break the constraints of the traditional single-dimensional research paradigm. For the first time, it integrates rural flash flood resilience and ecosystem regulating services (ERS) into a unified framework to explore the spatio-temporal evolution of their coupling and coordination relationship. [Methods] Taking Southwest Sichuan, a region characterized by frequent flash floods and critical ecological status, as the study area, we employed the Pressure-State-Response (PSR) model to construct the rural flash flood resilience evaluation system. Ecosystem regulating services, specifically soil retention and water yield, were quantified using the Modified Universal Soil Loss Equation (RUSLE) and the Water Balance Equation, respectively. Finally, the Coupling Coordination Degree Model was utilized to quantitatively analyze the synergistic relationship between the two systems from 2013 to 2023. [Results] (1) The level of rural flash flood resilience significantly increased from 0.343 to 0.471 during 2013–2023, yet a stable spatial pattern of "high in the north, low in the south" persisted. (2) ERS correlated with the hydro-thermal pattern but showed non-linear fluctuations influenced by climate, resulting in significant regional differentiation. (3) The coupling coordination relationship exhibited pronounced functional differentiation and spatial polarization. The coordination between rural flash flood resilience and soil retention was generally better, demonstrating wider and more stable spatial coverage. However, coordination with water yield was severely polarized: the northern areas maintained "High-Quality Coordination," while the Liangshan hinterland in the south remained in a long-term state of "Moderately" or even "Severely Dysfunctional." This highlights that the improvement of water yield service is subject to stricter natural endowment constraints, resulting in a limiting factor effect. [Conclusion] Future strategies for enhancing rural flash flood resilience must avoid a "one-size-fits-all" approach. We propose that coordinated regions in the north should focus on quality and efficiency improvement, while dysfunctional regions in the south should prioritize filling key gaps and implementing flood-adaptive restoration, specifically by promoting drought-tolerant vegetation combined with terracing to achieve coordinated development of the human-water-soil system.