Abstract: The research results of high precision sequence stratigraphy in the Liaozhong Sag of the Liaodong Bay Basin are used to build up detailed sedimentary sections that can exhibit the subtle sandbodies,and Temis2D software of IFP is employed to model the subtle reservoirs forming process for the first time.The results indicate that the modeling outcome is consistent with the drilling activities,which shows the subtle reservoir modeling is feasible.The modeling results reveal:the subtle lens reservoirs in Shahejie Fm in the Liaodong Sag of the Liaodong Bay Basin were formed by primary migration while the stratigraphic reservoirs were formed by secondary migration;the forming time of the subtle reservoirs in Shahejie Fm is relatively earlier than that in Dongying Fm;subtle reservoirs in Shahejie Fm were mainly formed at the final stage of Dongying and early stage of Guantao,but the forming time of some subtle reservoirs far away from the hydrocarbon kitchen were delayed due to the long distance migration.The subtle reservoirs in Dongying Fm were formed by the conduits of fault pathways and secondary migration,some were formed by the conduits of micro-crack or primary migration with the result of overpressure surpassing the seal pressure.The subtle reservoirs within Dongying Fm were formed later than those within Shahejie Fm,most were formed at the time of about 12 Ma,but some far away from the hydrocarbon kitchen were even formed after 6 Ma.Moreover,the forming of subtle reservoirs in this basin is related to the pathway system,lateral seal and top seal,the oil and gas would leak under the conditions of the open conduit and poor seal characteristics.