The Ti-80Al (wt. %) composite was deposited by cold spraying of Ti/Al mixture powder and a Al matrix composite reinforced with in-situ TiAl3 intertermtallic particles was prepared through annealing treatment of the above-mentioned cold-sprayed Ti/Al deposit. The microstructural evolution of TiAl3/Al composite during annealing treatment were investigated by Scan electrom microscopy (SEM), Engergy disperse spectroscopy (EDS) and X-ray diffraction instrumentor. The solid diffusion reaction between Ti particles and Al particles in the annealed Ti/Al deposit was studied and the in-situ formation mechanism of TiAl3 intermetallics was investigated. Results found that the as-sprayed Ti/Al deposit exhibited dense microstucture and had the same phase constitutes with that of the feedsock powder. The solid diffusion reaction between Ti particles and Al particles occurred in the local area of Ti/Al deposit when annealed at a temperature of 450oC and consenquently formed in-situ TiAl3 intermetallics. With increasing annealing temperature, content of TiAl3 intermetallics continuously increased. After annealing at 600oC, all Ti particles in the Ti/Al deposit had completely transformed into TiAl3 intermetallics, as a result, the Al matrix composite reinforced with in-situ TiAl3 intermetallics partices was prepared.