Abstract: The analysis of the sedimentary microfacies in the second member of the Hetaoyuan Formation,Nanyang depression is based on the cores,well logs and relevant analytical data.Two sets of sedimentary facies have been distinguished: the meandering stream-delta facies including the subaqueous distributary channel,channel mouth bar,distal bar and interdistributary bay microfacies in the northern part,and alluvial fan facies including braided channel and braided interchannel microfacies in the southern part.The hydrocarbon accumulation is dominantly controlled by the sedimentary microfacies cited above.The reservoir quality is best in the subaqueous distributary channel and braided channel sedimentary microfacies,followed by channel mouth bar and distal bar.