Abstract: Dabancheng Sub-depression is a secondary structural unit of Chaiwobao depressionof the Juggar basin. Due to influence of the Yanshanian movement, the area wasseverely faulted and six structural belts were formed. Local block anticlines,controlled bythrust faults, were finally in their fixed forms during the Himalayan movement.There is petroleum geological condition for formation of middle and small oil and gasfields in Dabancheng sub-depression according to the evolution of source rocks and its relationship with formation time of local structure and faults. Chaiwobao fold zone was themost favorable hydrocarbon-bearing structural zone, and Xigeda-Shanshuidi and TudunziXigouxiasi fold zones were potential ones. Meanwhile, the regional Upper Triassic andLower and Middle Jurassic seals were developed on the structural zones, thereby a circularhydrocarbon-rich belt was formed around the center of the subdepression.