Abstract: In terms of the examination of thin sections and scanning electron photomicrographs, combined with mercury injection test, micron-scale CT Scanning technique, X-ray diffraction analysis and fluid inclusion analysis, the present paper deals with the petrological features, physical properties of the clastic rocks, diagenesis and its effects on the reservoir quality, and prediction of the potential favourable zones based on the diagenatic facies analysis for the Meishan Formation in the Songnan-Baodao depression, Qiongdongnan Basin. The clastic rocks in the study area consist dominantly of fine-grained feldspathic quartz sandstone and siltstone, with point-line contacts and grain-supported textures. The cement types contain clay minerals and carbonate minerals. The porosity types are composed of intergranular solution openings, residual intergranular solution openings and intragranular solution openings, with fine-to extra-fine throats, and mesopores and low-to extra-low permeability. The destructive diagenesis is represented by compaction and cementation while the constructive diagenesis includes dissolution. The delta front may be the potential favourable zone for the development of the effective reservoir rocks in the Meishan Formation in the study area.