Abstract: Karst caves are valuable locations for studying prehistoric human activities during the Quaternary Period. Analyzing the depositional characteristics and provenance of clastic deposits in karst caves is crucial for understanding the evolutionary history of the depositional environment and shedding light on past human behaviors. Xiaodong Cave in Cangyuan, Southwest Yunnan was studied to unveil the source of clastic sediments. The grain size and mineralogical features of various clay minerals within and around the cave were analyzed. Results show that the cave sediments came mainly from the sediments in higher places outside the cave through sheet flow as shown in grain size characteristics. In addition, a small amount of insoluble material from limestone and materials formed after further weathering and pedogenesis were also accumulated. Overall, there might be four periods of further weathering and pedogenesis. Moreover, there were limestone breccias and rock debris fallen off from cave walls, from which four events of accumulation of limestone breccia or debris were recognized. The latest accumulation was obviously affected by human activities, to which sufficient attention should be paid in research works.