The kinetics of microstructural transformation has been analyzed using an endquenching and extinguishing method for a Ti50at%Al alloy synthesized by combustion. It is shown that from start of aluminum powder melting, a series of transition reactions takes place one after another as follows: Ti+Al1/3TiAl3+2/3TiTixAl+(1-x)TiTiAl. The liquidsolid reaction at the early stage may heat the sample quickly, which can create a good condition for later solidsolid reactions. Since masstransfer during solidstate diffusion is much slower than that within liquid reactants, the later solidsolid reactions slow and some Ti core is left in the alloy for rapid cooling. The aluminum contents of the boundary layers of the Ti cores are higher than those of central parts of the Ti cores, and the boundary layers transform into annular 2Ti3Al phase during cooling.