The dissolution of geological formations containing gypsum can rapidly create various karstic features, and may potentially generate great risks such as subsidence and collapse [1]. To understand the gypsum dissolution mechanism is very important to develop safety measures. It is not feasible to take into account all the pore-scale details at a large-scale by direct numerical modeling, and some sort of macro-scale models are essential. Such a macro-scale porous medium model can also serve as a diffuse interface model to describe the dissolution at a fluid/solid interface, as done in [2]. The objective of this study is to develop a macro-scale model, starting from the pore-scale transport problem with boundary condition corresponding to non-linear reaction or thermodynamic equilibrium, making use of the method of volume averaging [3], and then implement it for a large-scale cavity dissolution modeling.