Abstract: A cross section across the Lower Cretaceous Nanxin Formation was measured in the Yunlong region, western Yunnan. In the light of lithology,sedimentary structures and sectional architectures, the sedimentary facies in the Nanxin Formation mostly consist, from the base upwards, of the meandering stream and lake facies interbedded or intercalated with thin palaeosol facies. More precisely, the meandering stream facies may be subdivided into the channel, point bar, overbank and natural levee subfacies; the lake facies may be subdivided into the littoral lake, shallow lake and bathyal lake subfacies, and the palaeosol facies may be classified as two types of the calcareous soil and gley soil. The sedimentary facies sequences and associations indicate the variations in regional tectonics from relative active to stable tectonics, and the subtropic semi-arid to arid palaeoclimates during the deposition of the Lower Cretaceous Nanxin Formation.