Abstract: The development characteristics of continental sedimentary systems and the prediction of favorable reservoirs during the rifting period in the Weixi'nan Sag are key issues of research for hydrocarbon exploration in this area. Taking the third member of the Liushagang Formation (Liu-3 Member) in the Weizhou A Block as an example, we integrated sedimentology and diagenesis analyses to reveal the evolution patterns of sedimentary systems and the main controlling factors on favorable reservoirs. Results show that during the deposition period of the Liu-3 Member, braided river delta deposits controlled by mainly a transfer zone were developed in the study area, and 4 types of sedimentary microfacies were recognized: subaqueous distributary channels, interdistributary bays, mouth bars, and sheet sands. The evolution progresses went through three stages: development, flourishing, and decline, and the sand bodies reached the climax 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 were formed in two mechanisms: the sedimentary facies was the primary factor on the matrix properties and the diagenetic facies was the secondary that modified the reservoir rocks; and subaqueous distributary channels exhibit optimal physical properties, while dissolution is the primary constructive diagenetic process. By analyzing the coupling of geological and geophysical factors, we predicted that the sand bodies in the main area of the subaqueous distributary channels in the delta front will develop the most favorable reservoirs with higher exploration potential. The findings provided a theoretical foundation for future hydrocarbon exploration and development in continental lake basins.