This study is concerned with investigation of forming Ti fiber reinforced TiAl3 composite by infiltration-in situ reaction. The as-cast material was obtained by pressing molten pure Al into a preform which was composed of Ti particles and Ti fibers. Based on the differential scanning calorimetry (DSC) result, in situ reaction samples were obtained by heating as-cast materials to 660, 950, and 1300 A degrees C, and held for 1 h, respectively. The microstructure evolution of in situ reaction samples was analyzed by scanning electron microscope and Energy dispersive X-ray (EDX). In addition, the phase composition of products was inspected by X-ray diffraction (XRD). Experiment results show that TiAl3 was formed initially, which was the unique product between Ti and Al. While at high temperature, products of Ti fibers and Al were complex, and Ti (x) Al1-x (0.25 < x < 0.75) compounds were formed around Ti fibers. Finally, TiAl3 decomposed, and oxidation occurred. The mechanism of in situ reaction between Ti and Al in this system was discussed.