A Ti-C-Fe powder mixture with a finer Ti powder was used for a combustion front quenching test to investigate the effect of titanium particle size on the mechanism of the combustion reaction, and the microstructural evolution in the quenched specimen was then observed with scanning electron microscopy, and the combustion temperature was also measured. The results showed that the nature of the combustion reaction could be described with a dual-solution-precipitation mechanism and a correspondent model. The melting of the finer Ti particle prior to its reaction was attributed to a combined effect of two factors: a decrease of its size-controlled melting point, and a decrease of its composition-controlled melting point. The use of the finer Ti powder led to a more complete combustion reaction and hence a higher combustion temperature. As a result, the combustion-synthesized TiC-Fe cermet had a greater average size of TiC particles and layer-shaped pores that was confirmed to be a consequence of gathering of the evolved gases into the combustion wavefront.