Abstract: Quasi-soft soil is one special kind of soft clay with different characteristics in its formation,distribution,physical composition from other common sediments.Therefore,landslide occurred in the quasi-soft soil should have its own characteristics.The strata lithology,geologic structure and hydrogeologic features of the landslide are demonstrated by a case study at the K108 quasi-soft soil landslide along the Beijing-Zhuhai highway.Five slip surfaces and shape of slip bed of the landslide are identified by displacement monitoring.It was concluded that rainfall and slope excavation are two primary causes for landslide.