The large scale NWW striking Kalamaili fault zone in the eastern Junggar area is situated along the collision boundary between the Yemaquan and Harlik arcs, and along the southern margin of the Kalamaili ophiolite zone. On the basis of detailed field investigation and structural analysis, it is demonstrated that the NNE dipping Kalamaili fault zone is subjected to earlier brittle—ductile dextral shearing and later brittle thrusting in the orogenic procesess. The more easily deformed rocks in the Kalamaili brittle—ductile shear zone, such as slate, sandy slate, and low grade tuff, show densely foliation and tensile veins, and marls is deformed into mylonite. Deformation temperatures of the Kalamaili brittle—ductile shear zone is 250~300℃, and the shear zone development and regional low grade metamorphism of pre Permian volcanic—sedimentary rocks in this area occur at the same period. The second phase activity of the Kalamaili fault zone is top to the south thrusting. The thrusts formed along the foliation of the earlier shear zone, or truncated the earlier shear zone. A variety of geological phenomena show that the Kalamaili brittle—ductile dextral shearing took place in the middle Late Carboniferous. The shear zone results from the oblique collision between Yemaquan arc and Harlik arc, which suggests that the Kalamaili oceanic plate subducted northwards. The Kalamaili brittle thrusts formed in the Middle Permian and belong to intracontinental deformation happening after the post collisional extension of the area. This phase of deformation should be related to the Middle Permian collision within the Central Asian Orogenic Belt .