There are many landslide disasters in Yunnan Province of China. Many problems of landslide stability occur during the course of constructing highways in Yunnan Province too. It is proved to be crucial in the analyses of landslides stability to obtain the more exact parameters of slip surface. Firstly

the content and the main research method of the parameter analysis of slip surface are held up. Secondly

when the stability of basalt landslide on a highway in Yunnan Province is analyzed; in-site test are adopted to obtain the parameters of slip surface

because sliding mass of basalt landslide are loosen and sampling is difficult. Lastly

the robust regression analysis method is used to deal with the test data and calculate on the parameters of slip surface. Compared with other routine methods

the robust regression analysis method can reduce availably the effect of abnormal value

and then the results are more credible. Furthermore

it is pointed out that the restorations of residual shear strength on time effect are considered on analysis of the parameters of the fossil landslide slip surface.