In view of the multi-stage construction and reconstruction of complex structure of Bayanhushuu fault depression in the western fault depression of Hailaer Basin,there are not only various fault blocks and nosing structures of various origin,but also different types of hydrocarbon accumulation modes.In order to improve the success rate of oil and gas exploration in complex fault depression,based on the theory of light hydrocarbon microleakage,microbial-geochemical detection technologies,including Microbial Quick-Screen(MQS),Microbial Oil Survey Technique(MOST)and Sorbed Soil Gas(SSG)dection are applied to directly detect the change of microbial value and acid desorption hydrocarbon anomaly on the surface of the favorable exploration target area,predict the oil and gas properties of the underlying favorable target area,and identify the distribution range and oil and gas properties of the oil and gas reservoirs.The results show that there is a good correlation between the distribution of microbial anomalies and the known oil and gas areas and oil and gas wells,which indicates that the microbial-geochemical detection technology has good applicability and reliability in the Bayanhushuu fault depression of Hailaer Basin.The MOST+SSG technology combination is applied to further identify the favorable anomaly area,and it is considered that the western steep slope of Bayanhushuu fault depression is a long-term oil and gas advantageous accumulation area with large microleakage intensity.It is pointed out that the two nosing structures in the western steep slope belt are favorable areas for further oil and gas accumulation.