The work aims to obtain the relationship of solid-liquid interface energy changing over time during the reaction wetting process and master the core problem of reaction wetting kinetics. Theory derivation: during reaction wetting process, three-phase energy was in dynamic equilibrium at reaction interface. Based on this, new phase coverage rate a at the reaction interface and the fraction of interface active element occupancy concentration Fs were taken as two variables so that Young‘s equation and the boundary conditions could be used for mathematical derivation. Dezellus‘s cosθ-t relationship dynamic equation was also used for further theoretical derivation. Experimental verification: NiSi alloys were refined by vacuum melting furnace, and wetting experiments on graphite substrate were carried out in a high temperature vacuum humidifier by modified seat drop method. Change of contact angle during the reaction wetting process was recorded by a high resolution CCD camera to get contact angle data. The kinetic equation was verified by the data and formula. Through theoretical derivation, kinetic equation of the relationship between solid-liquid interface energy and time was derived. This equation was the same as the equation with instantaneous difference of solid-liquid interface energy as driving force during reaction process, and also identical to the equation derived by the Dezellus‘s cosθ-t relationship. In the kinetic equation, the solid-liquid interface energy was exponentially reduced over time. Results of wetting experiment by Ni-Si/C system showed that solid-liquid interface energy decreased exponentially with reaction time during the interface reaction control stage, which was consistent with solid-liquid interface energy changing with reaction time in the theoretically derived kinetic equation. Moreover, the activation energy of interfacial reaction of Ni-45wt%Si/C system was calculated to be 239 kJ/mol in combination with the kinetic equation and Arrhenius equation, which was close to the value reported in literature. The reaction kinetics equation is reliable in reactive wetting process. The relationship between solid-liquid interface energy and time is exponentially reduced, which can provide a theoretical reference for surface modification and wettability in coatings.