Abstract: The Iritish belt, served as one of the most important tectonic boundary in Central Asian Orogenic Belt (CAOB), extends more than 2 000 kilometers from west Siberian, through Ust-Kamenogorsk and Zhaisang Lake in Kazakhstan, Chinese Altai and then into Mogonia. In combination with systematic geochronological data, the detailed field observation along the Iritish belt in Ust-Kamenogorsk have been reported in this paper, aiming to have a better understanding its tectonic evolution process.The data reveals that amphibolite-facies metamorphism of the gneiss in this belt took place during 460~400 Ma, representing the Caledonian orogenic event. The gneissic granitesintruded into the gneiss along the lamellar structure and crystallized at ca.282 Ma, while the massive granodiorites sharply cut across the schistosity, with crystallized age of ca.252 Ma. Based on these observations, the evolution process of the Iritish belt can be divided into three stages at least, i.e., the Caledonian orogenic event (460~400 Ma), the Permian sinistral strike-slip and the Triassic magmatic event possibly related to the Siberia mantle plume.