In this study, coating-layer growth kinetics were determined to understand coating-layer growth behavior of Si pack cementation coatings on Mo-3Si-1B (wt%) alloys. When a pack powder mixture composed of Al2O3, Si and NaF was loaded in an alumina crucible with a substrate, a MoSi2 outer layer formed with a MoB phase between the outer layer and substrate. The average growth constant coefficient (k(0)) was estimated to be similar to 1899 mu m/h(1/2), and the activation energy for the growth rate of the coated layer thickness was estimated to be similar to 80 kJ/mol in the examined coating temperature range. The experimental results well matched the proposed equation for the growth kinetics of the coated layer on Mo-3Si-1B alloys. The oxidation behavior of the coating layer was also discussed in terms of the structural analysis.