Abstract: On the basis of fine stratigraphic correlation, sedimentary facies analysis and interlayer distribution pattern study, facies controlled three-dimensional geological modeling is carried out for the reservoirs in the southern region of MN Oilfield in Bohai Bay. In the simulation, phased facies control and quantitative characterization of reservoirs spatial distribution pattern are made according to the simulation mode either for "sandstone intercalating mudstone" or for "mudstone intercalating sand sandstone", taking the model as a clue, combined random simulation technology together with deterministic understanding, making sure the distribution of sedimentary subfacies and mudstone intercalations predicted from well data and seismic data, as well as the characteristics and differences of reservoir development in each sedimentary subfaces. The research shows that it will better reflect sedimentary understanding and improve the accuracy of reservoir modeling, if facies-controlled modeling is adopted with multi-conditional geological constraints, on the basis of fine geological characteristics.