Abstract：Slope destroy is a progressive process. During the process of formation of the shear bands，the shear strength parameters have different decay rates. So the margin of safety is different for parameters c and . The different softening characteristics of different soils were analyzed. The softening damage is found in the cohesive soil slope as formation of the shear bands，so the decay rate of cohesive c is more rapid than that of internal friction angle . The dilation and softening are disclosed in the sand soil slope，like the formation of the shear bands. The decay rate of internal friction angle is more rapid than that of cohesive parameter c. According to the different decay rates of parameters ，the modes of in the cohesive soil and in the sand soil were put forward. The different modes in the different soils were discussed to offer some references to relevant studies in geotechnical engineering.
