Abstract: Xinyan landslide caused by the new filling embankment，is a kind of partly superficial slide that is recently developed from a large ancient slide. The landslide soil has typical expansive property through mineral composition test and dilatability test on the landslide. This article analyzes the specific characteristics of the expansive soil from the slide shape，slide soil property and landslide deformation，and the genetic type of landslide is analyzed from four aspects of expansive soil，artificial filling，space of lateral deformation and water effect. This provided scientific proof for the supporting structure design of the landslide and played an extremely significant role in deeply studying and treating other expansive soil landslides in this region.

Key words: Landslide, Expansive soil, Filling embankment, Mechanism analysis