Abstract:Based on the comprehesvie analysis of previsou research results, the study concludes that the Que'ershanYinganshan area, which is to the north of Hongshishan fault belt in Beishan Mt., Gansu province is an island arc associated with subduction ocean crust and records the geological process of the subduction of the ancient Asian Ocean crust subducted into the southern margin of East Tianshan old land. The conclusion is based on the facts as follows:① this area is lack of ancient continental crust basement; ② subducted ocean crust relicts are indicated by volcanic rocks contained various age strata ranging from midOrdovician to Devonian and CarboniferousTriassic intermediateacidic intrusions. These rocks are represented by some calcalkaline rock association or TTG or adakite series; ③the evolution process of ancient Asian Ocean, which began with immature arc island, followed by mature island arc and ended by continental marginal arc, was successively testified by volcanic rock associations such as basalt, andesite and dacite in midOrdovician and Silurian, dominated by andesite and dacite interclating rhyolite in Devonian, and parts of high K calcalkaline rock association of intermediateacidic intrusions in Maanshan and Xiaocaohu in Triassic. Furthermore, it is suggested that the south subduction zone of ancient Asian Ocean should be really located in Mongolia, and the island arc zone should belong to part of continental margin accretionary terrain of East Tianshan old land.