Combined with the characteristics of the asymmetry failure mode of the two-layer clay foundation near slope and layered properties, the unilateral sliding failure mode of two-layer foundation under strip footing adjacent to slope was built on the basis of the existing relevant researches. The failure mechanism was formed by many sliders. According to speed compatible relationships and triangle closed condition, the corresponding planar kinematically admissible velocity field was constructed. By introducing the upper limit analysis theory, the ultimate bearing capacity calculation model of strip footings over two-layer foundation soil was derived. A new approach for determining the ultimate bearing capacity of two-layer foundation under strip footing adjacent to slope was put forward by using sequential quadratic programming optimization algorithm. By the use of Matlab symbolic operation function and optimization function, the finite element numerical analysis results were analyzed and compared with programmed calculation. The feasibility and rationality of the proposed approach was shown.