Abstract: The anticline, fault and other structures of Triassic — Jurassic have not very developed in the southeastern slope zone of the northwestern margin of Junggar Basin. but there are nine types of sedimentary facies, thirty subfacies and nearly one hundred microfacies. They are arid fan. humid fan. braided river, meandering river, anastomosed river. fan-delta. braided delta. lacustrine delta and lacustrine floor fan. etc. The changes of lithofacies are frequent. and there are lots of unstable components and types of diagenesi with greatly changes in the elastic rock. Also. there were well developed stratigraphic pinch out, overlap. and unconformity. which make the area have the essiential geologic conditions that formed the concealed oil-gas trap. There were four types of concealed traps.perhaps existing in Trassic-Jurassic of the lithological trap. paleomorphologic trap and mixed trap. According to analysis of structural and s叫1- mentary characteristics of the northwestern margin in Junggar Basin, there were all concealed oil-gas trap in north and south of Karamay-Wuerhe fault and Wuerhe Xiazigai fault. but the most favorable are should be north slope zone of Manas Lake depression to south of Well Guaill4-Well241--Well Ba.165 —Well134 Well Xia40.

Key words: Northwestern margin of Junggar Basin, Concealed oil gas trap, Sedimentary facies, Oil -gas pool type