Abstract: The strong heterogeneity and complex genesis are observed in the Maokou reservoir of the Middle Permian in Sichuan basin. There are lots of disputes about the understandings of the main controls on reservoir development and reservoir distribution, which brings great trouble to the exploration of Maokou formaion. Using the data of field sections, drilling data in the neighboring area and seismic exploration, the paper demonstrates the reservoir genesis of Maokou formation in Sichan basin from 3 aspects such as lithfacies paleogeography, reservoir characteristics and seismic reservoir prediction. It is considered that the Maokou formation is in the great gentle-slope sedimentary system of carbonate rocks; large-scale shallow-water high-energy reef-flat facies belts occur in western Sichuan basin, which can verify the existence of great deep faults penetrating from Permian strata to basement in Jinma-Yazihe structural belt and Longquanshan buried structural belt; dissolved pore-cavity reservoir and hydrothermal dolomite reservoir may be widely developed in the reef flat sediments at the top of Maokou formation under the actions of both unconformity karstification and fracture-related hydrothermal dolomitization. The above 2 types of reservoirs are the key favorable zones for large-scale gas reservoir exploration in Makou formation in western Sichuan basin