Abstract: The sedimentation of the Qiongzhusi Formation shale in the Sichuan Basin is controlled by the tectonic-sedimentary differentiation of the Deyang-Anyue Rift Trough. Its lithofacies types and distribution are closely related to sedimentary environments. Based on previous studies of the Qiongzhusi Formation, this research comprehensively uses core observation, thin-section identification, and geochemical testing and analysis to classify the lithofacies types of the Qiongzhusi Formation shale in the middle segment of the rift trough, and discusses the high quality shale lithofacies types and their distribution controlled by sedimentary environments. The results show that: (1) The sedimentary environment within the rift depression exhibits distinct differentiation characteristics. The central part of the depression is dominated by biogenic high-silica deposits, forming a strong reducing environment with a dual-threshold boundary, where ancient productivity and water retention reach their peak.; the trough margin is dominated by terrigenous clastic input. Horizontally, it shows a gradational pattern of "oxidizing margin-anoxic trough," while vertically, it exhibits a cyclic evolution of "anoxic at the bottom-dysoxic in the middle-oxidizing at the top." (2) "TOC-mineral-grain size" coupling lithofacies classification system is established, dividing 36 lithofacies types. It is clarified that 16 lithofacies types develop in the middle segment of the rift trough, such as organic-rich felsic shale (H-F-S) and organic-rich mixed silty shale (H-M-SS), systematically revealing the heterogeneity characteristics of shale and providing new ideas for predicting deep shale gas sweet spots. (3) The high-quality lithofacies are mainly organic-rich felsic shale (H-F-S), organic-rich mixed shale (H-M-S), organic-rich felsic silty shale (H-F-SS), organic-rich argillaceous silty shale (H-A-SS), and organic-rich mixed silty shale (H-M-SS), which are concentrated in the deep-water shelf facies of the 1st, 3rd, 5th, and 7th sub-layers of the Qiongzhusi Formation. The deep-water dysoxic-anoxic environments promote organic matter enrichment and preservation, and high felsic mineral content provides high-quality reservoir spaces. The research results provide key geological bases for the evaluation and development of deep shale gas resources in the Sichuan Basin.