Abstract: A large scale of mountain rock avalanche occurred at about 20:40 on July 23, 2019 in Jichang town, Shuicheng county, Guizhou Province. The rock mass moved down and scraped the original loose deposits and finally formed deposits of 191.2×10⁴ m³. It destroyed parts of Pingdi Village, resulted in the death of 43 persons and missing of 9 persons. Based on site investigation, unmanned aerial vehicle(UAV)photography and other technologies, this paper provides a detailed description on the characteristics and a comprehensive analysis on the dynamic process and failure mechanism of the long runout landslide. And there is still a risk that the accumulation of the landslide can be translated into debris flow during rainfall. The results indicate that the special geometry of the source area, the weathered and shattered basalt mass and favorable combination of discontinuities are the internal cause factors for sliding. The rainfall infiltrating and its softening effect, and the road construction cut-slope are the external cause factors for the landslide. There is no obvious signal before the occurrence of Jichang landslide. The masses have a long runout distance of 1300 m. When it occurred, it demonstrated the characteristics of confidentiality and strong paroxysm. It caused great danger in large range. There can be a big attribution if such case can be studied further. It can provide the significant experience on dealing with this kind of masses failure and how to provide advice on early warning and remediation project on similar cases in southwestern mountain areas of China.