Abstract： Red-soft-mudstone layer landslides of Jurassic，Cretaceous and Tertiary are widely distributed in north China. The basic characteristics of red-soft-mudstone layer are weak anti-weathering ability，low rock mass strength，and bad engineering geological property. The layer is very sensitive to water，and landslide hazards in the area of red-soft-mudstone is very serious. Geological environmental conditions of the red-mudstone layer landslides are the key factors for forming landslides. Rock mass strength characteristics determine the mechanics and deformation mechanism of landslides. The traits and moving characteristics of red-mudstone layer landslide are varied with different conditions of deformation and failure. Based on the study of rock mass strength in different conditions and shear strength of rock layer surface，the mechanisms of creep deformation and slip plane forming are systemically analyzed. The strength-controlling forecast method of critical landslide along red-soft-mudstone layer is given after statistic analysis on typical examples of red-soft-mudstone layer landslide.
