Because of the previous researches on occurrences of shale gas and the influencing factors of gas-bearing property being insufficient, combined with shale microstructure characteristics, pyrolysis simulation experiments on enrichment capacity of hydrocarbon gas have been systematically carried out with different types of shale at different mature stages, under different lithostatic pressure and fluid pressure and with different geological characteristics. It indicates that the extracted gas amount in shale, being relatively large, is closely related to their thermal maturity, namely the extracted gas productivity is very large at over-mature stage.