The hydrocarbon source and reservoir conditions of the gas reservoir of the second member of Xujiahe Formation in Sumatou structure are good. So oil and gas preservation conditions are the key factors to exploration in this area because the reservoir experienced multi-tectonic movement. On the basis of previous research results，factors related to hydrocarbon preservation conditions were analyzed comprehensively such as caprock condition，fault activity periods，pressure exerted on fault zone and geochemical characteristics，etc. The results show that the sealing ability of regional caprock of the second member of the Xujiahe Formation in Sumatou structure is excellent and the macroscopic seal of the direct caprock is good.The vertical sealing of different control gas faults is different，and the vertical sealing of the Fault M① is the best. Based on comprehensive analysis on the factors of caprock，fault and geochemical characteristics，etc.，it is concluded that the preservation condition of the gas reservoir of the second member of Xujiahe Formation is mainly controlled by the fault in Sumatou structure. Due to the destruction of the Fault M④，the preservation condition of the gas reservoir of the second member of the Xujiahe Formation in the upper wall of the Fault M① is poor，but that of the gas reservoir of the second member of the Xujiahe Formation in the footwall of the Fault M① is relatively good.