Abstract: Through geological investigation and field monitoring of Ningming tertiaryi limnic weathered mudstone and residual soil cut slopes of Nanning-Youviguan,Express the characteristics of water content,temperature,shrinking coefficient,swelling quantity variation under 50 kPa with depth of natural slopes and cut slopes in swell and shrinking active zone of expansive soil were studied.In connection with the correlation analysis between swell and shrinking fissure of slopes and behavior of landslides,a half-quantitative failure model for landslides of swell & shrinking active zones was proposed.It could provide reference to effective engineering treatment.