Abstract: With regard to foundation bearing capacity evaluation related to the basal stability of deep excavation and high filled steep slopes, the weak points of the methods in current engineering practice were discussed, and then an improved calculation method was proposed with reference to the idea first presented by Terzaghi. The improved method took account of the shear stress on the vertical fracture surface in the slope, and made it clear that the foundation bearing capacity should be calculated according to the unilateral slip failure mode, and adopted the more suitable second definition of the safety factor. A complete set of formulas was given, and its rationality and accuracy were validated through comparative calculations with the much refined method of finite element limit analysis.