AbstractStructures and various properties of refining slags can be estimated by the use of classical molecular dynamics simulation. The appropriateness of the estimation depends on the interatomic potentials used in the simulation. If modeling of the interatomic potentials is sound, the parameter values in the potential functions become equivalent to physical property values and their evaluation based on fitting of calculated properties with the measured values becomes equivalent to the measurement of the “physical properties”. This situation is also applicable to thermodynamic modeling. Once the parameter values, i.e. the “physical properties”, are evaluated by the use of some measurements or ab initio calculations, the simulation by the use of the model and the model itself have the ability of estimating a wide range of properties of refining slags. In this scope, a molecular dynamics approach of molten CaO‐SiO2, an evaluation method of energy parameter values in the Cell Model as a slag thermodynamic model by the use of NMR measurements are discussed. Estimation of viscosity and relative molar volume of slags by the use of thermodynamic properties is also mentioned.