The situation and process of landslide of Nanyu have been described. Based on the internal and the externalcause of the landslide .its cause of formation have been analysed. It is indicated that the landslide in Nanyu.Zhouqu county, depends on an ancient landslide that was formed in brocken zone in faulting structure.New landslide formed within ancient one. Before it slided，there were four times of heavy and storm rainfalls，which isan important action of formation of inducing landslide. The volume of the landslide reached 8. 7 million m3. The landslide blocked up the Beilongjiang river for 8 hours. The S 313 highway in front of the landslide was destroyed in the range of 2 km. The traffic transport was stopped up to 40 days. Harmfullness caused is quite serious.