The high organic matter content serves as the material foundation for oil and gas accumulation in lacustrine fine-grained sedimentary rocks. The enrichment of organic matter typically exhibits layered and banded structures, with significant spatial heterogeneity, posing great challenges for the exploration of terrestrial shale oil, the study of shale oil reservoir formation mechanisms, and cost management during development. Therefore, the key scientific issues such as the mechanisms of organic matter enrichment and its heterogeneous distribution in terrestrial shale oil and gas reservoirs require further discussion. This review of the sources, deposition, and burial processes of organic matter highlights its complexity, which is influenced by the diversity of organic matter types. The entire process involves intricate biochemical and electrochemical reactions. Furthermore, the review explores the vital impacts of factors such as paleoclimate, paleomedium, and paleogeography on the production, decomposition, preservation, and dilution of organic matter. Based on the geological characteristics of China’s terrestrial shale oil and gas basins, three models of organic matter enrichment in lacustrine fine-grained sedimentary rocks are identified: the saline water depression "productivity" model, the saline water fault depression "mixed" model, and the freshwater depression "preservation" model.