Abstract: Middle and lower Es³ and upper Es⁴ dark shale was previously considered as the main source rocks in Baxian of Central Hebei Province.Middle and lower Es⁴ dark shale with great thickness was discovered through the drilling of Well Xinglong-1.It is indicated through detailed geochemical study on this set of dark shale that its organic carbon content is 0.6%～6%,pyrolysis hydrocarbon generation potential 0.5～14mg/g and organic matter type Ⅱ₂-Ⅱ₁.It is obvious that it is medium-good source rock.It is indicated through organic matter maturity research on source rocks in Well Xinglong-1 that its maturity threshold is at 3200m,oil generation peak at 4700m and condensate and wet gas generation at about 5100m.In Well Xinglong-1,middle and lower Es⁴ dark shale has entered into the stage of condensate and wet gas.Therefore,this set of source rocks has hydrocarbon generation capacity.Basin simulation approach is used to measure hydrocarbon resource of middle and lower Es⁴ in the Baxian Sag,and the petroleum resource incremental is 22 million tons and natural gas resource incremental is 56.1 billion cubic meters.Thus,deep layer exploration in the Baxian Sag becomes more important.