High- energy shoal subfacies grainstone widely develops in Middle Permian Maokou carbonate shallow gentle slope in the western part of Sichuan Basin. Effected by Dongwu uplifted movement, karstic reservoirs developed in this region due to intensive hypergenic karstification at the end of Maokou age. Several sets of thick and good source rocks, such as Middle Permian Qixia and Maokou carbonate rocks, and thick Liangshan mudstone rock, developed during Middle Permian epoch. Every set of source rocks reached to the fastigium of hydrocarbon generation in succession and supplied great hydrocarbon potential. Two types of reservoirs develop in the middle to upper parts of Maokou Formation, one is fractures-void (or fractured) and another is dolostone pore. Drilling and outcrop data reveal both of them are of good gas-bearing potential. The favorable exploration area is in the superimposed zone of high-energy shoal with palaeokarst slope. The preservation condition is good due to the widely developing regional cap rock. It is deemed that there is good gas prospecting in Maokou Formation.