Recently, self-propagating high-temperature synthesis (SHS), related to metallic and ceramic powder inter- actions, has attracted huge interest from more and more researchers, because it can provide an attractive, energy-efficient approach to the synthesis of simple and complex materials. The adiabatic temperature Tad and apparent activation energy analysis of different thermit systems plays an important role in thermodynamic studies on combustion synthesis. After establishing and verifying a mathematic calculation program for predicting adiabatic temperatures, based on the thermo- dynamic theory of combustion synthesis systems, the adiabatic temperatures of the NiO/Al aluminothermic system dur- ing self-propagating high-temperature synthesis were investigated. The effect of a diluting agent additive fraction on combustion velocity was studied. According to the simulation and experimental results, the apparent activation energy was estimated using the Arrhenius diagram of ln(v/Tad)~1/Tad based on the combustion equation given by Merzhanov et al. When the temperature exceeds the boiling point of aluminum (2,790 K), the apparent activation energy of the NiO/ Al aluminothermic system is 64 ± 14 kJ/mol. In contrast, below 2,790 K, the apparent activation energy is 189 ± 15 kJ/ mol. The process of combustion contributed to the mass-transference of aluminum reactant of the burning compacts. The reliability of the simulation results was experimentally verified.