Abstract: The paper studies the second,the third and the forth sand sets member of Shuangjiang zones in Biyang depression,and analyzes the sedimentary microfacies,proves that this zone can be devided into eight sedimentary microfacies:underwater distributary channel,river mouth bar,interdistributary bay,nearshore underwater braided channel,farshore underwater distributary channel,microfaices between deltas,distal bar,sheet sand.The distribution of reservior in this zone is dispersal,and the condition of reservoir formation is not ideal,and reservoir is primarily river mouth bar,distributary channel sand and sheet sand.