Abstract: By using comprehensively analytical methods of casting thin sections identification,physical property and so on,the reservoir characteristics,sedimentation and diagenesis of Ziliujing formation Zhengzhuchong segment in Yuanba area northeast of Sichuan have been studied.The result indicates that: Ziliujing formation Zhengzhuchong segment developed into two sets of reservoir as conglomerate and sandstone.The the conglomerate reservoir′s reservoir space is mainly fracture,with fewer microporous and extremely low porosity and permeability,it is typical pore-fracture reservoir.Sandstone reservoir′s reservoir space is mainly the primary intergranular hole,the intergranular dissolution pore,intra granular dissoluted pore with few micro fracture,the average porosity is 6%,average permeability is 0.1×10(-3) μm2,it is pore reservoir.The development of Ziliujing formation Zhengzhuchong segment is affected obviously by sedimentation and diagenesis,which is mainly manifests in the following several aspects: the advantageous sedimentary facies belt decide different type reservoir′s plane distribution,the green mudstone′s existence promoted the sandstone reservoir growth degree,the corrosion is the important factor to form the good reservoir and the structure breakage is the key factor to form the good reservoir.