The Bonan Oilfield is located in the Bonan Sag ofJiyang Depression, and is a deeply buried low permeability faulted lithologic reservoirwith the largest oil reserves in Shengli Oilfield of Shandong Province The main oil bearing strata are in the Member 2 and Member 3 of Shahejie Formation of Paleogene with a low to middle porosity and a low permeability The low permeability reservoir is characterized by its complex genetic mechanism By employing the concept of diagenetic reservoir facies, the evaluation of reservoir quality in the third area of Bonan complex oilfield was made in order to predict the distribution of effective reservoir and its storage capacity more accurately The research on sedimentary facies and diagenesis of the reservoir combined  withanalyses of diagenesis effect of low permeability reservoir on the reservoir property and with the division of diagenesis stages indicates that the geneticmechanism of the low permeability reservoir in this area is the filling and cementation of autogenetic mineral during diagenesis Using seven chosen parameters including flow zone index, porosity, permeability, median grain size, mud content, median pore throat radius and variance coefficient, and applying cluster and discriminant methods, four kinds of diagenetic reservoir facies were classified Combined with the analyses of their characteristics and sedimentary facies, the timespace distribution is also givenOur result provides a guide to the development of low permeability oilfield[WTHZ]