Abstract: The development characteristics of continental sedimentary systems and the prediction of favorable reservoirs during the rift period in the Weixi'nan Sag are key issues constraining hydrocarbon exploration in this area. This study takes the third member of the Liushagang Formation ( Liu-3 member) in the Weizhou A Block as an example, integrating sedimentology and diagenesis research to reveal the evolution patterns of sedimentary systems and the main controlling factors of favorable reservoirs. The results show that during the deposition period of the Liu-3 member, braided river delta deposits controlled by a transfer zone are mainly developed in the study area, with 4 types of sedimentary microfacies identified: subaqueous distributary channels, interdistributary bays, mouth bars, and sheet sands. Its evolution progresses through three stages: development, flourishing, and decline, with the sand bodies reaching their largest scale during the flourishing stage. The reservoirs are predominantly low-porosity and low-permeability quartz sandstones, with secondary dissolution pores constituting the dominant reservoir space. Quantitative evaluation results clearly indicate that favorable reservoirs are controlled by a dual mechanism of “sedimentary facies governing matrix properties and diagenetic facies governing alteration”: subaqueous distributary channels exhibit optimal physical properties, while dissolution is the primary constructive diagenetic processs. By analyzing the coupling of geological and geophysical factors, it is predicted that the sand bodies in the main area of the subaqueous distributary channels at the delta front will develop the most favorable reservoirs with higher exploration potential. These findings provide a theoretical foundation for future hydrocarbon exploration and development in continental lake basins.