[Objective]The Member 2 of the Meishan Formation in the Lingshui Sag, Qiongdongnan Basin, hosts a distinctive mixed siliciclastic-carbonate rock assemblage, whose unique characteristics make it a natural laboratory for investigating the differential evolution mechanisms of mixed reservoir rocks. However, the strong reservoir heterogeneity and unclear distribution patterns of high-quality reservoirs in this interval have constrained deep-water hydrocarbon exploration. [Methods] Based on cast thin sections, scanning electron microscopy, and porosity-permeability data, this study systematically analyzed the mixed lithofacies types, diagenetic processes, and pore evolution characteristics, revealing the coupling mechanism of "depositional fabric-diagenetic response-reservoir quality" that controls the differential evolution of reservoirs. [Results] The results indicate that: (1) Three types of mixed lithofacies developed in the study area with significant differences in depositional fabric: Type I lithofacies (sandy foraminiferal limestone) is matrix-supported with abundant lime mud and biogenic shells; Type II lithofacies (bioclastic calcareous-cemented sandstone) is grain-supported with high sand and bioclastic content; and Type III lithofacies (bioclastic lime-muddy sandstone) is matrix-supported with low grain content. These depositional fabric differences established the material foundation for diagenetic evolution. (2) The three lithofacies types exhibit distinct diagenetic-pore evolution pathways: the dissolution-dominated porosity enhancement type (Type I lithofacies) experienced early compaction and cementation leading to dense rock, followed by significant late dissolution and porosity enhancement, forming high-porosity (17.25%) quality reservoirs; the cementation-dissolution composite type (Type II lithofacies) underwent strong early cementation causing porosity reduction, with limited late dissolution, forming medium-porosity (14.53%) moderate-quality reservoirs; and the compaction-dominated porosity reduction type (Type III lithofacies) experienced continuous compaction and densification with weak dissolution, forming non-reservoir intervals (8.45%). (3) Quantitative restoration of pore evolution across the study area indicates that compaction reduced porosity by 8.57%, cementation reduced porosity by 4.31%, and dissolution increased porosity by 9.79%, resulting in a final porosity of 13.54%. [Conclusion] The "depositional fabric-diagenetic response-reservoir quality" coupling mechanism revealed in this study elucidates the intrinsic laws governing the differential evolution of reservoirs in deep-water mixed sedimentary environments. Depositional fabric determines the type, intensity, and temporal combination of diagenetic processes, thereby controlling reservoir quality, providing a generalizable theoretical paradigm for mixed rock reservoir prediction.