Lake ecosystems in arid and semi-arid regions play a pivotal role in deciphering how climatic dynamics and associated catchment processes modulate lake functioning. However, research on the responses of lake ecosystems in northeast China to large-scale climate oscillations since the deglaciation remains scarce. Here, we present a high-resolution paleolimnological record from Hulun Lake, the largest freshwater lake in northern China, derived from subfossil diatom assemblages and multiple geochemical and physical proxies, to examine how the lake ecosystem responded to East Asian Monsoon variability and local environmental changes since -17.0 cal kyr BP. The diatom record demonstrates that the lake ecosystem exhibited a highly sensitive and long-term response to post-deglacial climatic changes, predominantly mediated by climate-driven hydrological shifts and catchment processes. During Heinrich Event 1 (H1; 17.0-15.0 cal kyr BP), diatom abundance was generally low, with early community shifts toward benthic Fragilaria taxa and heavily silicified Aulacoseira granulata, which reflect the water level, likely triggered by enhanced meltwater inflow. Between 15.0 cal kyr BP and 11.0 cal kyr BP, rising temperatures coincided with increased lake levels and nutrient availability. A. granulata showed a transient increase, whereas cold-tolerant Fragilaria species reached peak abundances during the Younger Dryas (12.9-11.7 cal kyr BP). At the onset of the Holocene (-11.7 cal kyr BP), warming climate facilitated the extensive proliferation of A. granulata, while cold-water Fragilaria taxa declined sharply. During the mid-to-late Holocene, lake productivity increased, evidenced by elevated diatom concentrations, associated with nutrientrich conditions (TN, TOC). Redundancy analysis (RDA) emphasizes the strong indirect effect (temperature) of Holocene climate change on diatom community composition via hydrological and catchment-mediated pathways. Collectively, diatom variations in Hulun Lake over the past -17,000 years were shaped by climatic changes, which mediated shifts in lake productivity, water level, and trophic status, among which water level and trophic status are the primary driving factors. Our findings demonstrate that climate exerted an overarching control on the lake ecosystem, providing critical insights into the linkages between large-scale monsoonal variability and lake functioning in semi-arid northern China.