The carbonate platform margin is an important gathering place of large-scale oil and gas resources, and the study of paleogeographic differentiation is the basis to reveal the characteristics and development laws of the carbonate platform margin. Following the discovery of a trillion square meter natural gas gold accumulation zone in the platform margin reef-beach facies of the Upper Permian Changxing Formation in Sichuan Basin, the platform margin beach reservoir of the Middle Permian Maokou Formation has recently been discovered, and several open flow wells of more than one million square meters have shown great exploration potential. However, there are significant differences in sedimentary filling and reservoir characteristics between these two periods, and detailed comparative analysis will help deepen the understanding of carbonate platform model and its reservoir control effect. Based on a large number of drilling, field outcrop and seismic data from the Sichuan Basin and its surrounding Permian system, the typical sedimentary facies and lithofacies paleogeographic pattern are analyzed, and the differences between the two types of platform margins are compared. The results show the differentiation from shallow-water platform to deep water shelf by multiple synsedimentary faults occurred in Permian paleogeography of Sichuan Basin from Maokou period, with Kaijiang-Liangping trough being the most typical. The shallow-water carbonate platform of Changxing Formation is characterized by the development of thick platform margin reef-beach facies, and the shallow-water carbonate platform of Maokou Formation is characterized by the development of thin platform margin beach facies, both of which rapidly change into siliceous rock and carbonaceous shale. The Maokou period belongs to the initial geomorphic inherited platform margin, which is represented by several thin beach bodies with intermittent accretion under the background of wide margin. In the Changxing period, the platform margin was shaped by sedimentary border, showing a thick reef flat body with continuous accretion or prograding under the background of narrow margin. In general, both platform margins have the potential to develop large-scale reservoirs and are important targets for exploration of large oil and gas accumulation zones.