Corium cooling system plays an important role to prevent the interaction between the molten corium and concrete of a pedestal region. As the material for constituting the corium cooling system, zirconia-based refractory materials are promising due to its high melting points and chemical stabilities. To estimate the erosion depth of the refractory material in the severe accidents, we developed an interaction model for molten corium and zirconia refractory material based on the erosion mechanism. Our developed model were based on two main phenomena; reduction reaction of the zirconia refractory material and oxygen diffusion in the zirconia. On the interface of the molten corium, oxygen in the zirconia are extracted by the reduction reaction. On the other hand, in the zirconia, oxygen are transferred to the interface according to Fick's laws of diffusion because the reduction reactions induce concentration gradient of oxygen in the zirconia. Thus, the erosion rate of the zirconia are governed by the reduction reaction and oxygen diffusion. We modeled the erosion behaviors as three phase: (1) just reduction reaction phase, (2) transitional erosion phase, (3) steady erosion phase. As a result, we found that our model grasp the trend of the erosion behaviors. As the future works, we require to investigate the temperature dependency of the reduction reaction rate to evaluate more accurately.