Abstract: As the most important source rock for gas generation in the Sichuan Basin, Permian source rocks have attracted more and more attentions. The lithofacies palaeogeography during the Longtan phase of the Late Permian in the Sichuan Basin was reconstructed, and the controlling effects of sedimentary environment on source rock generation were analyzed. In the Upper Permian of the Sichuan Basin, favorable source rocks mainly developed in the shallow shelf, tidal flat-lagoon and onshore swamp facies. The concept of "organic carbon thickness" was introduced in this article. Organic carbon content was multiplied by source rock thickness so as to illustrate the generation features of source rocks. Combined with inorganic geochemical characteristics and organic carbon analyses, the controlling effects of sedimentary environment on source rock generation were studied, providing theoretical reference for the macroscopic distribution prediction of source rocks and resource estimation.