Abstract: Aiming at the fact that the extra - low permeability reservoir in middle Shanbei slope is affected by some factors such as sedimentary environment、diagenesis, tectonics etc, which leads the property of reservoir sedimentary facies becoming extremely complex. Using well - log curves, this paper analyzed active relationship among stratum information and all genetic signs and hydrody- namic factors in relevant sedimentary environment, and made research on logging facies, sedimentary microfacies and distribution and development of reservoir sand body, by which it is confirmed that the underwater distribution channel microfacies and channel overlying debouch bar microfacies of delta front subfacies could be regarded as the favorable facies for forming low permeability reservoir sand body, which can control the striking and distribution of sand body, while it has the characteristics of fine continuity, connectivity, and high thickness. Through the research on Chang332 reservoir sedimentary microfacies and favorable oil - bearing area prediction in studied area, it can be known that the reservoir lied in middle and southwest host facies of underwater distribution channel belongs to five water systems which developed from northwest to southeast, the favorable oil - bearing area reservoir which controlled and blocked out by favorable deposi-tional facies entirely characterized to be more upgrading from middle to southwest lower middle reaches. All of this can provide reliable foundation for future rolling and border expanding exploitation of the reservoir in this area.