Abstract: The engineering properties of carbonaceous mudstone may be significantly reduced when water is introduced, which can easily cause engineering problems. A landslide project was used in this paper to study the role of carbonaceous mudstone stratum in the formation of landslide. Data collection, on-site investigation and laboratory test were used to investigate the occurrence environment and basic characteristics of the landslide area. According to the causes of landslide development, we analyzed the formation mechanism, and concluded that the main factor for the formation of the landslide is poor hydrologic characteristics of carbonaceous mudstone stratum, and the main inducing factor is the continuous rainfall. On this basis, we analyzed the slope stability qualitatively and quantitatively, and concluded that the slope will continue to slide under the rainfall conditions and should be treated as soon as possible. According to the characteristics of the landslide, we introduced a comprehensive treatment scheme to contral this landslide, including anti-slide pile, crack fillup, intercepting ditch, retaining wall and displacement monitoring.