Abstract: The research on the natural gas reservoir-forming geologic factor of northern Hebei depression indicates that in the area，there are two sets of well developed hydrocarbon source rocks which are Lower Tertiary lacustrine mudstone and carboniferous-permian coal beds，including five sets of favorable reservoirs such as Wumishan marine carbonate rocks，Cambrian-Ordivician marine carbonate rocks，Permian Sandstone，Lower Tertiary Conglomarate and Lower Tertiary Sandstone.There are four sets of aeral cap rocks developed in from Upper paleazoic-cenozoic，such five types of natural gas genesis are grouped into biogas，biological thermal-catalytic gas，pyrolysis gas，biologic-reforming gas and coal bed methane according to the maturity，geochemical indicators and structural features of explored gas.The conditions of reservoir formation are favorable.By means of the analysis of the reservoir-forming association and tectonic settings of differenty types of gas，the three sets of gas reservoir-forming systems in northern central Hebei depression are identified，they are in deep and shallow formations of Langgu Sag and deep formation of Baxian Sag.Eight types of gas reservoir-forming models are put forward.It is indicated that two reservoir-forming systems in Langgu Sag and Baxian Sag are prospective ones.There are three favorable targets in Niudong deep buried hills，Daxin conglomerate body and Suqiao-Wen′an buried hills.

Key words: gas source rock, reservoir-forming system, genesis of natural gas, reservoir-forming model, inner buried hill