Submicrometric TiB2 powders were synthesized by carbothermal reduction process using titanium dioxide, boron carbide and carbon black as the starting materials. The influence of different amount of boron carbide (22.0–26.8wt%), calcination temperature (1400–1900°C) and holding time (15–90min) on the composition and microstructure of the product was investigated. The resultant powders were characterized by X-ray diffraction (XRD) and scanning electron microscope (SEM). Results showed that hexagonal impurity-free TiB2 crystalline powders with the grain size below 1.0μm could be successfully prepared at 1600°C for 30min in Ar atmosphere when the amount of boron carbide was 25.3wt%. The increase in temperature contributed to reaction completion and grain growth, but the abnormal grain growth and oversintering took place above 1800°C.