Abstract: Estimate of strength parameters of rock-soil-structure is a necessary work of numerical simulation and sta-bility calculation of pile foundation, excavation pit and slope with the retaining structure. In the paper formulae calcu-lating uniaxial tensile and compressive strengths of the retaining structure(pile) are derived from coordination condition of deformation., and formulae calculating cohesion and internal friction angle of rock, soil and the re-taming structure(pile) are derived from four combination conditions of two-dimensional and three-dimensional stresses with failure criterions of Mohr-Coulomb' inclined line and Mohr's parabola, finally deviation is dis-cussed. The study result has the important theoretical significance and the practical value of engineering.