A simple method, which uses numerical calculations to estimate diffusion fluxes into reactive interfaces during silicide formation processes, has been developed. Based on analysis of calculated diffusion fluxes from experiments from five different published papers, a model has been proposed to explain the unique kinetic behavior associated with thin‐film metal‐silicon diffusion couples. The reactive interface in a metal‐silicon diffusion couple is considered to be a reaction region, and the reaction process is divided into three steps. Several physical quantities have been defined to describe each of these steps, i.e., the diffusion flux of moving reactant to the reaction regionJm, the release rate of nonmoving reactantrn, and the formation rate of the growing phaseF. The relationship between these quantities has been demonstrated by means of a reaction process plot, which is also developed in this study.