Two kinds of volcanic rocks have been recognized in the central part of east Tianshan Mountains. One is andesitic volcanic rock along the Aqishan island arc(II2)，and the other is basaltic volcanic rock in the melange zone of the Qiugemintashi trench( II1).Volcanic rock formed in each tectonic setting has its unique gcochcmical features that can be matched with the setting. Volcanic rocks in this region are comparable with the volcanic rocks formed in the region of typical tectonic settings in such aspects as major elements, trace elements and REE. Based on the different geochemical features, the authors consider that: volcanic rocks in the Aqishan island arc(II2)were mainly in conjunction with the subduction of Tulufan oceanic crust into Tarim continental crust in early Carboniferous, being mainly calc-alkaline volcanic rocks. Basaltic volcanic rock, which occurred as a piece of oceanic crust in the melange zone of the trench( II2)，was mainly associated with the extension of Tulufan oceanic basin, belonging to oceanic tholeiite.