There is a set of marine Silurian tight clastic rock with sedimentary thickness of 1000~1450 m in Jiannan Gas Field and its surrounding area in west Hubei-east Chongqing. It is the important formation for oil and gas exploration in southern China. Observation of field outcrop, description of core samples and analysis of (cast) thin-sections indicate that the Silurian reservoir rock commonly consists of very fine grained feldspathic quartzose sandstone and lithic quartzose sandstone with abundant quartz which has a relatively high maturity in composition and texture. The reservoirs are mostly of TypeⅢand less of the TypeⅠand TypeⅡwith low porosity and low permeability. Secondary intergranular dissolved pores are the common type of porosity.