Abstract: Aiming at the magmatic sources of Late-Palaeozoic granites from Tianshan, this paper comprehensively and systemically discusses the representative granites from various tectonic units of Tianshan according their Sr、Nd、Pb isotopic characteristics, and reveals many obvious differences in these granites. On the basis of comparison with the isotopic characteristics of their wall rocks, the potential sources of these granites are indicated. The Late-Palaeozoic granites in Carboniferous to Permian rift belt of Jueluo tage have the highest ΕNd(t)values and the lowest(⁸⁷Sr/⁸⁶Sr)t values,and the island-arc volcanic rocks(juvenile crust)of Devonian Dananhu Formation may be the potential source of Permian granites represented by the quartz diorites in Kangguer;the Late-Carboniferous to Permian granites of Bogda area are probably the products of the partial-melting of the contemporaneous basic volcanic or underp lating basic magma.