High temperature interfacial evolution by reaction between liquid Al and solid Ti3Al has been studied by observation of reaction couples isothermally reacted at 700, 800 and 900°C for different time intervals between 1 and 60 min respectively. Only TiAl3 phase was detected in Al/Ti3Al reaction couples up to 900°C. The reaction zone consisted of aluminide particles dispersed in an Al rich matrix. However, microstructures in the inner, central and marginal regions of reaction zone were different and were continuously changing across the width of reaction zone. A model corresponding to evolution progress was drawn schematically. A water quenched experiment confirmed the restriction effect of dispersed TiAl3 particles to Al matrix and suggested that TiAl3p/Al composite could be fabricated by this in situ reaction method.