Though Li isotope fractionation during mantle melting and differentiation of basaltic melts have been proved insignificant, Li isotopic systems during crustal processes remain unclear. To study this, we report combined petrological, Nd-Sr and Li isotopic data for the late Paleozoic coexisting I- and A-type granites in the East Junggar orogen of the Central Asian Orogenic Belt. The granites were formed responding to underplating of mafic magmas in the lower crust in a postcollisional, extensional regime, and intruded into the Paleozoic foldbelts that formed due to extensive oceanic subduction-accretion processes.