In order to better evaluate the treatment effect of the natural soft soil reinforcement, an elasto-viscoplastic constitutive model based on super-subloading surface has been used to describe the mechanical characteristics of the natural soft soil foundation. By using finite element method software ABAQUS, a simulation can be achieved of the layer-filled process of embankment, thus obtaining the bearing capacity and deformation characteristics of the soft soil foundation treated by block-rock compaction method. An analysis has been made of the influence of different thickness, modulus of deformation, different loading and filling time on the bearing capacity of soft soil roadbed and post-construction settlement and deformation. The results show that the elasto-viscoplastic constitutive model based on super-subloading surface can effectively simulate the deformation characteristics of the soft soil foundation, which can be used for post-construction settlement analysis of complex subgrade. Thickness and modulus of deformation of rock fill have significant effects on the bearing capacity of foundation. Moreover, thickness, length of filling and surcharge of rock fill have significant effects on post-construction settlement, while modulus of deformation of rock fill has no significant effect on post-construction settlement.