Based on the background mesh method commonly used in building concrete mesoscopic model, the mesh refinement technology of balanced quadtree was used to refine the local meshes of interfacial transition zone（ITZ）. The concrete mesoscopic model which is more reasonable for reflecting the constituent of ITZ is given, and the programmed implementation scheme of mesh refinement was studied. In the proposed concrete mesoscopic model, ITZ can be directly assigned as the corresponding material parameters, and the serrated imperfection of meshes of ITZ in the background mesh method is improved. Accordingly, the geometrical morphology and material property of ITZ are simulated much better and more truly. In the end, numerical example is presented to demonstrate the rationality and effectiveness of the proposed method.