Abstract: In recent years, although significant oil and gas discoveries have been made in the northern slope of Lingshui Sag, Qiongdongnan Basin, the main controlling factors of reservoir development in this area are still not well understood, which restricts further exploration and research. Therefore, this paper selects Meishan Formation, the main reservoir in this area, as the research object to investigate reservoir characteristics and the main controlling factors. Based on drilling and seismic data from the northern slope of Lingshui Sag, the sedimentary, petrology, reservoir space characteristics, and primary diagenetic processes of Meishan Formation reservoir are analyzed. The results indicate that Meishan Formation in the study area exhibits a complete third-order sequence stratigraphic character. Overall, it is characterized, dominated by slope fan subfacies depositional environment. The lithology is mainly fine sandstone and siltstone, with generally low permeability but relatively good porosity, which can be regarded as effective reservoir. The dominant reservoir space type is intergranular dissolution pores, and the main controlling factors of reservoir development are sedimentation and diagenesis.