Lake Dian, a typical plateau freshwater lake in China, has experienced increasingly severe eutrophication in recent years due to intensified human activities and continuous nutrient inputs. To elucidate the composition and sources of sterols in surface sediments of Lake Dian , this study conducted systematic multi-site sampling and analyzed the spatial distribution of sterol molecular markers, total organic carbon (TOC), total nitrogen (TN), and the C/N ratio, in conjunction with watershed land use patterns. The results revealed pronounced spatial heterogeneity in organic matter content and C/N ratios across the lake. The Caohai area, influenced by urban runoff and multiple river inflows, exhibited higher organic matter content and C/N values compared to Waihai, displaying a southwest-high, northeast-low gradient. In Waihai, deep central zones had greater organic matter content and C/N ratios than littoral shallow areas, forming a center-high, margin-low pattern. Sterol biomarker analysis indicated that C27 sterols (coprostanol, epicoprostanol, cholesterol, and cholestanol) were primarily enriched in Caohai and the northern and southeastern Waihai, reflecting significant inputs from domestic sewage and anthropogenic activities, C?? sterols, including coprostanol and epicoprostanol, were mainly distributed in Caohai, as well as in the northeastern and southern regions of Waihai, indicating strong influence from domestic sewage inputs. C28 and C29 sterols (campesterol, stigmasterol, and β-sitosterol) were enriched in Caohai as well as in the central and southern regions of Waihai,, indicating substantial higher plant inputs associated with intensive agricultural activity. C30 sterol (dinosterol) was notably elevated in the southern sediments, suggesting high dinoflagellate biomass. Overall, the integration of sterols with TOC, TN, C/N ratios, and land use analysis effectively reveals the spatial heterogeneity of autochthonous, allochthonous, and anthropogenic organic matter in Lake Dian sediments, providing a robust tool for eutrophication monitoring and pollution source apportionment in plateau lake systems.