Abstract: On January 22, 2024, at 5:21 AM, a rock avalanche event occurred in Liangshui Village, Zhenxiong County, Yunnan Province, China. The rock avalanche traveled up to 450 m, eroding the original slope cover along its path, and ultimately forming a deposit with an estimated volume of approximately 15.6×10⁴ m³. This tragic event resulted in the loss of 44 lives from 18 households. By conducting an investigation of the disaster site, utilizing UAV aerial photography technology, geotechnical sample collection and testing, among other methods, a comprehensive study was performed on the fundamental characteristics of the rock avalanche and the engineering geological conditions of the slope in Liangshui Village. Furthermore, the initiation zone region was studied to understand the mechanisms of rock mass instability in the source area and the dynamic processes following instability. It was found that the water content of the slope cover layer near the initiation zone reached up to 55.75%. The shear strength test results revealed that the shear strength index of the soil sample decreased by over 50% after 7 days of saturation; the shear strength test results also revealed that the shear strength index of the mudstone sample decreased by over 40% after 10 days of saturation. Analysis indicated that steep terrain, weathered and fractured bedrock, and developed relaxation cracks were the primary internal causes of slope instability. Additionally, frequent winter snowfall in the rock avalanche zone, followed by melting ice water infiltrating the slope interior, softened the rock and soil mass, significantly contributing to slope instability.