Abstract: Through reservoir characteristics analysis and controlling factor analysis of reservoir forming of Da'anzhai section in Langzhong-south area of north Sichuan,favorable sedimentary microfacies are considered to be the basis of reservoirs.The pores,fractures and caves formed by constructive diagenesis are considered to be the key reservoir forming factor,which is to say,the bio-fragmental beaches provide favorable permeable reservoirs.Through superposition of diagenesis fracturing and structural fracturing and multi-phases recrystallization and dissolution,the pore-fracture-cave developed reservoirs are formed.Strong reflection response characteristics have been displayed on seismic data. In combination with seismic data,the research on predicted hydrocarbon enrichment zone of Da'anzhai section in Langzhong-south area of north Sichuan has been carried out,which can provide guidance for next exploration and development.