According to the characteristics of the shiplock high slope of Three- Gorges Project, this paper simplified the rock mass of the high slope as orthogonally anisotropical media.On the basis of recongnizing the nonlinear mechanics of excavation unloading,the paper prsents the nonlinear mechanics calculating method ,the theory of changing stiffen analysis. The calculating results agree fairly close to the measured one.By the excavating calculation of shiplock high slope, the paper shows that the rock mass will produce the large deformations,which have the large difference with the results of the old studies