The growth mechanism in plasma-assisted chemical vapor deposition of titanium (Ti) from titanium tetrachloride (TiCl4) was studied by macrocavity analysis, optical emission spectroscopy and thermodynamic calculations. It has been found that there are two types of important reactions on a Ti surface : the etching process and the growth process. In the Ti etching process, there are two kind of etching species. One is the Cl atom produced in the TiCl4/H-2/Ar plasma which is an active reactant. The other is the source gas TiCl4, and the reactivity of this molecule is very low. In the growth process, TiCl3 appears to be the main intermediate molecule for Ti deposition. During Ti deposition both the etching and growth reactions occur concurrently.