The age and genesis of plagiogranite in Karamaili ophiolitic melange of Xinjiang are still in controversy. In this study, the geochemical characteristics and LA-ICP-MS zircon U-Pb ages of the plagiogranite were determined. It is found that the rare earth and trace element characteristics of plagiogranite in east Qingshui are different from those of plagiogranite and cumulate gabbro in ophiolite, but are similar to those of massive gabbro. The geochemical characteristics of plagiogranite in east Qingshui and massive gabbro also show partial melting trend. The age of plagiogranite in east Qingshui is(342.0±3.8)Ma, suggesting that it was probably the product of post-collisional tectono-thermal event in early Carboniferous rather than the leucocrate in ophiolite.