It is of significance to research failure mechanism of debris landslides that are widespread in the Three Gorges Reservoir Area. Based on the statistical analysis of the developmental law and failure mode of debris landslides in the Three Gorges Reservoir, the mode of progressive failure is found. The mechanical model for progressive failure of debris landslides with two slip bands is also established by applying slice method. According to the results of the downslide force between adjacent slices, if the downslide force of lower slice is larger than zero, the slice fails along the major sliding surface, otherwise it is stable. In result, the failure range is obtained. The stress function can be determined through dimensional analysis of failure slice. According to static boundary conditions of the slice, stress state of any point in the slice can be obtained. Then stress state of any point in the secondary slip band can also be established. The failure of the secondary slip band is judged on the basis of Mohr-Coulomb failure criterion. Therefore, a mechanical method is proposed to analyze the progressive failure of debris landslide with two slip bands. It is of significance to research failure mechanism of dryst landslides that are widespread in the Three Gorges Reservoir Area. Based on the statistical analysis of the developmental law and failure mode of doubles landslides in the Three Gorges Reservoir, the mode of progressive failure is found. According to the results of the downslide force between adjacent slices, the downslide force of lower slice is greater than zero, the slice fails along the the The result of the failure of the slice can be determined by the analysis of the static boundary conditions of the slice. The stress state of any point in the slice can be得到. Then stress state of any point in the secondary slip band can also be established. The failure of the secondary slip band is ju d, d on the basis of Mohr-Coulomb failure criterion. Therefore, a mechanical method is proposed to analyze the progressive failure of the debris landslide with two slip bands.