The Tahe oil field is the most typical large oilfield located in the Akkol salient of the Xayar uplift in the northern Tarim basin. Studies on trap elements, and formation and evolution of pools indicated that the regional characteristics of pools are of layer anticlinal pools controlled by the Akkol structure and karst. Analysis on the origin and combination of the trap elements, origin of traps and main features of the traps suggested that the Ordovician pools in the Tahe oilfield are carbonate pools of unconformity and karst palaeo-weathering crust.