Based on the comprehesvie analysis of previsou research results, the study concludes that the Que'ershanYinganshan 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 midOrdovician to Devonian and CarboniferousTriassic intermediateacidic intrusions. These rocks are represented by some calcalkaline 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 midOrdovician and Silurian, dominated by andesite and dacite interclating rhyolite in Devonian, and parts of high K calcalkaline rock association of intermediateacidic 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.