Several types of granites are distributed in Karamaili area of East Junggar, Xinjiang, which constitutes an important tin metallogenic zone.Biotite granites there have long been thought to be of S-type. Nevertheless, the study conducted by the authors shows that biotite granites in Sujiquan are actually typical aluminous A-type granites characterized by enrichment of LILE (such as Rb, K) and HFSE (such as Zr, Hf) as well as high FeO*/MgO and 10?000 Ga/Alratios. These features are obviously different from those observed for I- and S- type granites. Zircon U-Pb dating by LA-ICPMS shows that they were emplaced atabout 304±2Ma, close to the formation time of alkaline granites but later than the emplacement of calc-alkaline granitoids in this area. Although these biotite granites possess high εNd(t) values, they were not derived directly from a depleted mantle, but were most likely formed by partial melting of mantle-derived juvenile crustal materials which were subjected to deep burial and magmatic fractional crystallization. Trace element tectonic discriminant diagrams for granites reveal that biotite granites belong to post-collision granitoids, which marked the end of orogenic movement and the beginning of the intraplate evolution in Karamaili of East Junggar in late boniferous.