Abstract: Great breakthrough has been achieved in the second member of Shawan formation in Chunguang area of Chepaizi swell, Junggar basin. However，there are a lot of discussions about its depositional system. The uncertainty of its sedimentary facies adds some difficulties to fine description of sandbody and detailed study on sandbody internal configuration and reservoir modeling, which slows down the process of petroleum exploration and development for the lithological reservoirs in the area. Based on the data of core, logging, testing and high-resolution 3D seismic and the analysis of remote sensing images of modern sedimentary systems, the sandbody distributions in the area are compared with those of Maqu river in Gansu province and Lena delta in Russia. The results show that the second member of Shawan formation belongs to braided river delta sedimentary system, where braided river delta plain and braided river delta front are developed, the main sedimentary microfacies can be divided into distributary channel, underwater distributary channel and distributary sand bar and sandbodies are well developed. The reason of the formation of the lithological trap belt in the study area is the lateral continuity of the distributary channel and distributary sand bar resulted from the developed distributary bays, which leads to traps isolated from each other; it is hard to form efficient traps in the southeast of the area due to the lack of transverse breaks of deposits