To be able to accurately determine the main period of fault activity and its relation to the deep gas accumulation in the Xujiaweizi Depression, Songliao Basin, in this paper, four methods of syndepositional fault activity rate, volcanic activity period to determine fault activity period, stretch rate of cross section profile and tectonic evolution section are used to judge them successively. First, the research about the rates of syndepositional fault activity rate shows that the faults had been active during Lower Cretaceous Huoshiling Formation(Fm.), Shahezi Fm., Yingcheng Fm., the Second Member of Denglouku Fm., the Second Member of Quantou Fm. and Upper Cretaceous Qingshankou Fm.. Secondly, based on the matching relation between the volcanic activity period and fault activity, fault depression period (Lower Cretaceous Huoshiling Fm., the First Member of Yingcheng Fm. and the Third Member of Yingcheng Fm.) and the deposition of Upper Cretaceous Qingshankou Fm. are the main periods of activity for the faults. Again, from the section stretch, the periods of faults activities were Lower Cretaceous Huoshiling Fm., Shahezi Fm., the First Member of Yingcheng Fm., the Second Member of Quantou Fm., the Third Member of Quantou Fm., the Forth Member of Quantou Fm. and Upper Cretaceous Qingshankou Fm.. Finally, through the tectonic evolution history of the LINE1208, the major activity period of faults are Lower Cretaceous Huoshiling Fm., Shahezi Fm., the First Member of Yingcheng Fm., the Third Member of Yingcheng Fm., the Second Member of Quantou Fm. and Upper Cretaceous Qingshankou Fm.. Fault activity rates integrated judge concluded that there are 3 main periods of fault activity in the Xujiaweizi Depression and they are： Lower Cretaceous Huoshiling Fm.—the Third Member of Yingcheng Fm., Lower Cretaceous； the interim of Lower Cretaceous Quantou Fm. and Upper Cretaceous Qingshankou Fm.. They are analyzed the matching relationship of the fault activity main periods，the exhaust periods of gas source rocks, the formation of cap rock sealing ability and gas charging period in the Xujiaweizi Depression. Comprehensive study accounts that the sealing ability formed periods of 2 sets of important cap rocks, are earlier than source rocks gas generation period numerously, so cap rocks are not the factor constraining of gas accumulation，but the fault activity main period and gas charging main period is exactly the same period，and it is an important period of gas migration，and is also an important period deep of gas reservoir formation in the Xujiaweizi Depression. And after the formation of gas reservoir (K2y to the present) fault activity is weak, which is the main reason of gas reservoirs unspoiled and still relatively intact.