Abstract： The distinctive geographical and climatic attributes of Yunnan create advantageous natural circumstances for the evolution and advancement of prehistoric human populations.The investigation of paleoenvironmental conditions at the Sanhedong Locality,situated in the southern region of the Yunling Hengduan Mountain Range in Weishan,Yunnan Province,aims to examine the correlation between alterations in the environment and human behavior.The test excavations conducted in the Sanhedong Locality revealed a significant presence of animal bones within the stratigraphic layers.Furthermore,it was observed that the quantity of animal bones exhibited a progressive rise from earlier to later periods;AMS 14C results indicate that the Locality belongs to the Upper Paleolithic;The findings from the analysis of pollen indicate that during the early stage of Marine Isotope Stage 3(MIS 3)in the examined region,coniferous forests were the prevailing vegetation type,characterized by a notable presence of hemlock.Additionally,fern species such as Polypodiaceae and Pteris were observed in the understory.In the later stage,coniferous forests continued to dominate,but there was an increase in the abundance of understory herbs.The prevailing climate during this period was characterized by mildness and humidity.The lithic study reveals that a combined total of 15 stone artifacts,recovered from both the test trench and the ground surface,have similarities with the core-flake industry.This industry is closely associated with the gravel stone tradition observed during the Upper Paleolithic period in South China.According to the exhaustive research,the climate during MIS 3 was mild and humid,and the number of ancient human activities in the Sanhedong Locality gradually rose over time.In addition,the ancient people who lived in the Sanhedong Locality relied heavily on the meat and other products of animals as a primary source of food,whereas there was an interruption in human activity during the cold phase of MIS 2,demonstrating that the alteration of the ecological environment that was brought on by the variability in climate during the last glacial epoch had a significant impact on the activities of ancient humans.The finding of the Sanhedong Locality and the subsequent exhaustive study of it can give an essential reference for the investigation of the environmental adaption tactics utilized by ancient people in the Southwest China region during the Upper Paleolithic period.