Abstract: The kyanite-sillimanite type progressive metamorphic belt developed in Chonghuer area, Altai, Xinjiang,is composed of chlorite-biotite, biotite-garnet, garnet-staurolite, staurolite-kyanite and sillimanite zones. The metamorphic peak temperature and pressure of staurolite-kyanite and sillimanite zones are 560~680 ℃ and 4.4~5.8 kbar, respectively. There are abundant accessory monazites of metamorphic origin with high Th-U-Pb contents in rocks suitable for CHIME dating. The dating results show that the metamorphic age of these rocks is 268±10 Ma~ 261±20 Ma, consistent with the age of the andalusite-sillimanite type (low pressure type) metamorphism in Altai area, indicating that the kyanite-sillimanite and andalusite-sillimanite type progressive metamorphic belts were formed in the same regional tectonothermal event at Middle Permian. These ages provided the direct chronological evidence for the closure of the Paleo-Asian Ocean.