The synthesis of β-SiC cages, cubes, and nanoparticles using Yajima process which include reaction at the vapor-liquid interface was discussed. It was found that both precursors Pre-I and Pre-II were composed of mixtures of polycarbosilane and NaCl. The linear polycarbosilane was probably wrapped around the NaCl crystal completely in the Pre-I. It was observed that the difference between the precursors generated pronounced shape variations in the final products of β-SiC. Analysis shows that the difference in appearance between Pre-I and Pre-II is the consequence of of the difference in interaction between the phase-separated solid products generated at the interface of the vapor-liquid/solid reactions.