Abstract: To simulate the non-homogeneity of masonry materials, a two-phase numerical modeling strategy based on Cohesive elements is proposed. In the proposed method, masonry is considered as a two-phase material, which consists of stone blocks and mortar joints. Solid elements are used to simulate the blocks. A nonlinear constitutive model is introduced to describe their failure behavior. Cohesive elements are inserted between adjacent blocks to consider the shear and tensile failure of the mortar. The effectiveness and applicability of the method are verified by comparison of experimental tests and numerical simulation. The influence of sensitive parameters, such as the shear friction coefficient μ and loading position, on the strength of the arch bridge is analyzed by numerical simulation. The results show that the two-phase numerical model of stone masonry based on Cohesive elements avoided the difficulty in continuous numerical methods in simulating the non-homogeneity of masonry materials, and provided important information for the ultimate strength evaluation of stone arch bridges, such as the load displacement curves and failure modes. In addition, the failure mechanism of the main arch was determined by the bending and shear characteristics of the arches, especially the shear fiction coefficient of the mortar joints.