To check the stability of Dayantang landslide, the in-situ direct shear tests of both large areas and original undisturbed samples were carried out. Then, cohesionC and friction angle φ , which are the most sensitive geo-mechanicls parameters to the stability of landslide, were selected by using statistical analysis method and analogical method. Reasonable classification of testing results and standardization are the foundation of selecting parameters. This article puts for ward the variation coefficient of two-dimensional array, and calculates the parameter C,φ with statistic revision method. Their statistical significances are clear, and the parameters can be used effectively in practice.