The yield of silicon carbide strongly depends on the synthetic conditions. As it results from the literature search, thermodynamic modeling of SiC production using correct values of thermodynamic functions has not been carried out. In order to select the optimum synthetic conditions, the calculation of thermodynamic equilibrium in the system SiO2+nC has been performed under different conditions (p=const; V=const; n=2,3,5). Thermodynamic functions were evaluated on the basis of molecular constants of SiC, SiC2, Si3C, Si2C, Si2C2, selected during comprehensive analysis of the modem data on the structure of these molecules. The calculation of equilibrium compositions was made in the temperature range 1400-3000K. Here all possible components of condensed phases and gas phase have been taken into account. Isochoric process (V=7m(3)/kg) occurs in larger temperature range (1600-2000K); in addition, the decomposition of silicon carbide takes place to a lesser degree, and the concentration of silicon monoxide is considerably higher than that of other components (except CO). It was shown that in respect to SiC production, the isochoric process with ngreater than or equal to3 is the best choice.