By influence of early Indosinian movement, the middle Triassic carbonate rocks were generally subjected to denudation and karstification in western Sichuan Basin. Observation and geochemical analysis of cores and rock debris from several wells and outcrops show many distinct features of epikarstification on the upper part of Middle Triassic Leikoupo Formation. The paleokarstification created good conditions for reservoir development on the upper part of Leikoupo Formation. A set of porous karst reservoirs develops in the Upper Submember of Leikoupo 4th Member, which mainly consists of dolomicrite, crystalline dolostone, limedolostone, dolomitic limestone and algal dolarenite/calcarenite and is 38~75 m of accumulated thickness in Xinchang Gas Field. The Leikoupo 4th Member reservoirs are mainly Types Ⅱ and Ⅲ. It is deemed that the development of reservoirs is controlled by lithology combination, microtopography and burial karstification.