Abstract: Located at the northern end of the Yunnan-Myanmar-Malaysia-Thailand microcontinent, the Baoshan block is an important part of multi-island ocean in Paleozoic Tethys, western Yunnan Province. The oldest exposed stratum is known as the Gongyanghe Group on the Baoshan block. It is mainly exposed in two areas, i.e., Jiufang-Jiucheng-Dawangtang and Zhen'anjie-Raolangjie-Gongyanghe-Manhai-Ruili. It is a lithological association with huge thickness, consisting of sandstone, feldspar quartz sandstone, sandy slate and muddy slate, intercalated with siliceous rocks, argillaceous siliceous rocks, thin limestone, with the typical turbidity sedimentary characteristics and some low grade metamorphic features. Few fossils exist in the Gongyanghe Group, causing the lack of the chronological information, and hence its geological time was previously inferred to be Sinian to Middle Cambrian. In recent years, 1:250000 and 1:50000 regional geological survey conducted further research on Gongyanghe Group. A number of reliable LA-ICP-MS zircon U-Pb ages (925.0±9.2~500.0±1.0Ma) were obtained from newly discovered intermediate-acid volcanic lava and tuff interlayer. Combined with the differences of lithological association and sedimentary environment, it is suggested that Gongyanghe Group should be subdivided into 3 formations from bottom to top, namely Qingbaikou to Nanhua System Dawangtang Formation, Sinian-Middle Cambrian Gongyanghe Formation, and Early Cambrian-Ordovician Pumanshao Formation. This paper mainly describes the distribution, lithological association, sedimentary environment and geological epoch of the Dawangtang Formation.