This paper studies the sedimentary facies, the diagenetic reservoir facies and their origin mechanism in the deep zone of Shahejie formation in Gaoshangpu oil field. Based on the regional geology, the well logging, the sandstone slice, the casting slice, the scanning electronic microscope, and the X-ray diffraction methods, the sedimentary facies, the diagenesis and their influencing factors are studied. The diagenetic reservoir facies are classified and the origin mechanism is discussed. It is shown that the fan delta front deposition is developed, and the extensive distributive channels and mouth bars are the favorable oil accumulation locations. The effect on the reservoir property of diagenesis is analyzed, and it is indicated that the origin mechanism of the low permeability in this area is of the strong compaction, the infill and the cementation of autogenetic mineral during diagenesis. Based on the diagenesis study, the diagenetic reservoir facies are divided into four types and their characteristics are analyzed, including the secondary pores diagenetic reservoir facies with solution of unstable ingredients, the residual intergranular pores diagenetic reservoir facies with middle-strong compaction and cementation, the remaining intergranular pores diagenetic reservoir facies with strong compaction and cementation, and the tight diagenetic reservoir facies with extremely strong compaction and cementation. Using eight chosen parameters, that is, the flow zone index, the porosity, the permeability, the median grain size, the mud content, the expel pressure, the median pore throat radius and the variance coefficient, with the genetic artificial neural network method, the study and prediction models are established, and four diagenetic reservoir facies types are identified in the target formation. Combined with the analyses of the sedimentary facies, the time-space distributions of diagenetic reservoir facies are explained. The result may serve as a guide in the development of low permeability oil fields.