Abstract: The mylonited granite is located at Shenshuitan mining setion of Wulonggou area in the middle part of the East Kunlun, with a yielded LA-ICP-MS zircon U-Pb age of 389.7±3.9Ma. This granite has high SiO₂ (74.86%~76.64%), K₂O (5.20%~6.06%) and total alkali content (K₂O + Na₂O=8.05%~8. 83%) values. The samples are characterized by strong loss in Ba, Nb-Ta, Sr, P and Ti, as well as strong negative Eu anomaly (δ Eu=0.07~0.12), which shows characteristics of A type granite. Combined with the studies of Silurian-Devonian magmatic rocks in this studying area, it's proposed that the East Kunlun Orogenic belt has entered the post-collision stage in early Devonian, and the most intense of extension was happened in the conversion period of from early Devonian to middle Devonian, forming A type granite with considerable size, and standing for the end of the Caledonian orogenic cycle.