To determine the mechanism and conditions for the increased of product yield of titanium diboride TiB2 low temperature synthesis, a thermodynamic assessment of the interaction in the TiО2 – B2О3 – C system was performed. A numerical method was used to study a series of consequentially-parallel processes for the reduction of titanium oxide to its non-stoichiometric oxycarbide phase and its subsequent interaction with gaseous boron oxides. The Gibbs energy was estimated for oxycarbide TiCxO1 –x and titanium borate TiBO3 at 1027oC, which are related as GTiC0xO1–x >> G0TiBO3. This energy ratio of intermediate products of the titanium diboride synthesis allowed to make essential corrections in providing conditions and final results of synthesis. At the first stage of the process, it was established that fluorine-doped titanium oxide TiO2 –xFx is reduced to oxycarbide TiCxO1 –x with a deficient carbon content of x < 0.5. At the final stage, exposure of isolated system at a fixed temperature requires moderate kinetic stimulation of TiB2 synthesis by periodic vacuuming. This is due to the need to create conditions for the disproportionation of gaseous boron oxide B2O3(gas) to its suboxides (B2O2(gas), BO2(gas)) in the volume of the reaction mixture TiО2 – B2О3 – C and to suppress the “parasitic” reaction of the titanium borate TiBO3 formation. The established mechanism assumes observance of balance between temperature and duration of phase transformations during the exposure of the system at the first stage, a balance between the increased PB2O2/PCO ratio in the gas phase and the temperature at the final stage of the titanium diboride synthesis. The mechanism and conditions for the TiB2 synthesis are confirmed by laboratory experiments, the implementation of which allows to obtain titanium diboride powders of technical purity at 1030–1050oC.