Abstract: Several slope geohazards induced by continuous rainstorm occurred in Badong County on March 31, 2003, which resulted in destruction of many houses and casualties. On the basis of field investigation, the authors believe that the severe hazard mass on the Tongmuyuan slope belongs to a typical slope-type debris flow, i.e. the debris flow on slope. Its deformation characteristics and corresponding formation mechanisms are analyzed and the critical rain threshold value and early warning indices for predicting the rapid deformation of loose rock-soil masses on the shallow slope surface are discussed.