Abstract: The Sangonghe Formation on the eastern margin of the Junggar Basin,Xinjiang is divided,on the basis of cores,seismic data and well logs,into two third-order sequences J1SQ1 and J1SQ2,each of which may be involved into the lowstand,transgressive and highstand systems tracts. Two types of slope breaks are recognized in the seismic profiles and well-tie sections,including the textural and faulted slope breaks. The slope break system distributed in radial and latitudinal directions led to the development of the lowstand systems tract at the base of the Sangonghe Formation. Six sedimentary microfacies associations are arranged into three sedimentary microfacies association sequences in the Sangonghe Formation. The slope breaks in the steep slope zones are significant in that they may facilitate the development of the lowstand systems tract,in which the channel-mouth bar delta front sandstones in the steep slope zones are interpreted as the favourable areas for hydrocarbon accumulation.