To ensure the quality of large size castinges, production, of casting models on a laboratory scale is necessary as a preliminary step. The main object of this paper is to find, by performing a similarity analysis, the main criterial similarity groups to be preserved in the prototype and a small dimensioned model. The given similarity approach is based on a comprehensive mathematical analysis of the solidification process, heat transfer mechanisms and temperature differentials through the governing differential equations of continuity, momentum and energy. Applying mathematical techniques on these equations, the following dimensionless numbers were found to have a valuable importance : phase change number, superheating number, drift flux number and firiction number. The physical significance of these numbers are discussed and the conditions imposed by them in design of model-casting process are evaluated. The mentioned results are applied to a simple case for the process of casting simulation. Hence, interesting conclusions of the feasibility of this methed for modeling a casting process have been stated.