Abstract: The Scotia Sea is a critical region for the study of Antarctic Circumpolar Current. The sedimentary records of Scotia Sea reveal coupled environmental and biological responses to glacial-interglacial cycles over the past 160 ka. Based on diatom abundance, community composition, and biogenic silica content from core U1537, we reconstructed the paleoenvironment and diatom response mechanisms of the Scotia Sea. Diatom abundance and biogenic silica were significantly higher during interglacial periods (Holocene and MIS 5; 4.96×10⁷ valves/g) than during glacial intervals (MIS 2, 4, 6; 1.55×10⁷ valves/g). During glacial periods, an intensified Weddell Gyre led to expanded and prolonged sea-ice coverage, limiting light availability and photosynthesis, which resulted in a notable reduction in diatom abundance and biogenic silica content. In contrast, interglacial periods were characterized by elevated temperatures, sea-ice melt, southward intrusion of Circumpolar Deep Water, and a poleward shift of the Southern Hemisphere Westerlies. These environmental factors weakened vertical stratification and enhanced upwelling, thereby increasing nutrient supply to the surface and boosting productivity. Diatom community composition differed markedly between glacial and interglacial periods. Glacial intervals were dominated by sea-ice-associated species assemblages (e.g., Actinocyclus actinochilus, Fragilariopsis curta), while the relative abundance of open-ocean diatom assemblages (e.g., Fragilariopsis kerguelensis) increased significantly during interglacial periods, reflecting a southward shift of the Antarctic Circumpolar Current system and reduced water column stratification. This shift reflects the southward migration of the ACC and reduced water column stratification. These findings show that variations in diatom productivity and environmental evolution in the Scotia Sea over glacial-interglacial timescales during the past 160 ka were regulated by multiple factors, including temperature, sea-ice dynamics, changes in ocean current systems and nutrient availability, which underscores the close coupling between carbon cycling and climate dynamics in the Southern Ocean.