Abstract We report on the relationship between grown polytypes and the activity ratio of silicon to carbon during SiC solution growth using multicomponent solvents. From the thermodynamic calculation as well as crystallization experiments, we revealed that a high activity ratio (a _Si/a _C) in the solution leads to the growth of low-hexagonality polytypes, and low a _Si/a _C results in the growth of high-hexagonality polytypes. 4H-SiC is stable when a _Si/a _C is relatively low (∼10¹ > a _Si/a _C), 3C-SiC is stable when a _Si/a _C is relatively high (∼10⁴ < a _Si/a _C), and 6H-SiC is stable in the intermediate a _Si/a _C range (∼10² < a _Si/a _C < ∼10³). From these results, the Cr–Si solvent at high temperatures is expected to be suitable for 4H-SiC growth, and Sc–Si and Fe–Si solvents at relatively low temperatures are expected to be suitable for 3C-SiC growth.