In the context of global change and human activities, the increasing frequency of heavy rainfall and drought events due to uneven precipitation distribution poses significant challenges to ecosystem hydrology. Forest and grass ecosystems can exhibit distinct hydrological responses to climate extremes, yet their short- and long-term reactions across multiple temporal scales remain inadequately quantified. Using field standard runoff plots and vertically-distributed soil moisture monitoring systems over 13 years, this study investigated the effects of extreme rainfall events on P (precipitation), R (runoff), ET (evapotranspiration), and SWC (soil water content) in forest and grass ecosystems within a rocky mountainous area of Beijing. At the event scale, NG (natural grass) showed faster and more pronounced hydrological responses in shallow soil layers compared to SF (secondary forest). Storm events induced significant water transport in deep soils across both NG and SF. Deep water movement was regulated by root systems and pre-storm SWC, with SF demonstrating greater soil water retention capacity. At the annual scale, the primary water output was ET, accounting for 75.42% similar to 107.69% of NG and 78.68% similar to 121.55% of SF. Multi-year R was markedly higher in NG than in SF, although mean annual R accounted for only 6.74% to 12.97% of annual P. Deep SWC was significantly greater in extremely wet years compared to extremely dry years, highlighting the role of extreme precipitation in deep soil water recharge and retention. Both ecosystems exhibited multi-year soil water deficits, although heavy rainfall at the end of the growing season occasionally resulted in annual water surplus. These findings provide new insights into the hydrological dynamics of rocky mountain ecosystems under increasing climate variability.