The mechanism linking volcanism to anomalous organic matter enrichment in saline lacustrine basins remains unclear. Here, the second member of the Middle Permian Lucaogou Formation (P2l2) in the Malang Sag, Santanghu Basin, is examined using TOC, Rock-Eval parameters, biomarker proxies, mineral compositions, and major- and trace-element data. The P2l2 is divided into a non-volcanic activity stage (NVAS) and a stable volcanic activity stage (SVAS) based on tuff occurrence, volcanic material content (Vm), and rhythmic mineralogical variations. The two stages exhibit similar organic matter types and thermal maturity, indicating that these factors did not control the observed TOC differences. All anomalously high TOC intervals occur in the SVAS. Proxy data indicate that the NVAS was deposited under hot, arid, saline, shallow-water, and strongly reducing conditions in which organic matter enrichment was primarily controlled by preservation. During the SVAS, volcanic activity likely moderated the hot and arid climate, intensified chemical weathering, deepened the lake, reduced salinity, weakened persistent bottom-water reduction, and increased redox variability. At the same time, paleoproductivity increased significantly compared to the NVAS. Volcanism thus reorganized the lake system by modifying hydroclimate, basin hydrology, water chemistry, and nutrient supply, thereby shifting the dominant control on organic matter enrichment from preservation to productivity. These results provide a process-based explanation for volcanism-driven source-rock development in saline lacustrine basins.