Titanium diboride ( TiB₂) coating was successfully deposited on low carbon steel and graphite substrate respectively depending on TiCl₄-BCl₃-H₂reactive system by chemical vapor deposition technology. The effect of deposition temperature , gas flow rate and substrate material on microstructure and microhardness of TiB₂coating was researched. The result shows that , TiB₂coating, which was deposited on low carbon steel substrate, exhibit random grains and better crystallization at higher temperature, columnar grains at lower temperature and lower BCl₃gas flow rate characterized by XRD patterns and SEM observation . Microhardness test indicates that the microhardness value of TiB₂coating of random grain is higher than that of oriented columnar grains. The substrate material affects the deposition rate of TiB₂coating strongly. Deposited 1 h at 100 mL / min BCl₃and 980 ℃ , the thickness of TiB₂coating attains 44 μm ~ 70 μm at graphite surface whereas 20 μm at low carbon steel .