The effective thermal conductivities of porous coke - pitch mixtures were measured during cooling and heating processes. The thermal conductivity of the solid phase(lambda(s)) is estimated using a heat transfer model for a porous body. In the estimation, porosity was given based on experiments and thermal conductivity of gas phase is estimated using a pyrolysis model. The results demonstrated that lambda(s) is independent of temperature when no change in true density occurs, and that lambda(s) increases with increasing true density. lambda(s) is correlated with hydrogen content. The derived equation is used to predict the effective thermal conductivities of the mixtures and packed coals during carbonization. Pyrolysis models, heat transfer models and models describing macroscopic physical changes are constructed. The models agree with the experiments. This fact shows the applicability of the developed equation to coal.