Purification of naphthalene from naphthalene-rich oil of coal tar distillates was explored by using the melt and solution crystallizations. The solid-liquid equilibrium of naphthalene - benzothiopherre -methanol and naphthalene - benzothiophene systems were investigated. The crystal growth rates were characterized by supersaturation in solution crystallization and by the degree of subcooling in melt crystallization. The effective distribution coefficients of solution and melt crystallizations were compared by degree of subcooling at various cooling rates, and evaluated by the criterion of Wintermantel. The morphologies of crystals were compared in both solution and melt crystallizations. The solution crystallization using methanol proved to be the better technology to separate naphthalene from naphthalene-rich oil. The purity of the crystals has been upgraded over 99.9 wt% by a solution crystallization.