A new dynamics model describing the time-dependent change of solid–liquid interfacial tension is first established to explain the driving force and physical essence of the spreading process of reaction-limited wetting. The model has been successfully verified through the wetting experiments of Al–Si/SiC systems (Si content = 0, 7, 12 wt%, respectively) at different temperatures, in which the logarithmic plots of driving force versus time present a linear relationship in the reaction-limited spreading stage. Furthermore, the mechanisms of reactive spreading are discussed in detail.