In the Shuangjing area on the north of Xar Moron suture zone, there is a suite of rapid accumulation with low maturity, which were called ‘Kedehe conglomerate’ and previously divided into Middle Permian (Zhesi Formation) and Late Permian (Linxi Formation) respectively. Based on the previous research results, the authors made an another detailed study on the developed strata of Kedehe conglomerate rocks through field measurement. The results of the study of the LA- ICP- MS U- Pb geochronology of sandstone samples from the 1st, 25th and 86th layers of the section showed that they had similar primary age ranges. The age spectrum of detrital zircon falls mainly in three intervals of 485~405 Ma、463~401 Ma、520~363 Ma with peak ages of 427 Ma, 445 Ma and 440 Ma, additionally, the zircons accounts for 48. 0%, 52. 5% and 38. 8% of the total amount respectively. In the second place, the ages of ca. 1800 Ma and ca. 2500 Ma are more widely distributed, indicating the information of the North China Plate basement.The youngest peak ages of the three bottom- up dating samples are 312 Ma, 376 Ma and 282 Ma, and the youngest zircons are 304 Ma, 244 Ma and 245 Ma, respectively. Fossils of fusulinid and coral from the Late Carboniferous to Early Permian Amushan Formation were found in limestone gravel of the 85th layers of the section, and Mesozoic sporopollen fossils recovered from the 41st and 43th layers. According to the fossils and detrital zircon U- Pb age, the age of Kedehe conglomerate rocks can be classified as Middle Triassic. It is speculated that Xar Moron suture zone has experienced a long- time accretion and stitching process. The collisional collapse process between the North China plate and the Siberian plate occurred since the Middle Permian. The Paleo- Asian Ocean finally closed along the Xar Moron suture zone at least until the Middle Triassic, and the Kedehe conglomerate rocks are the product of collision on its both sides.