The polycarbosilane (PCS) precursor for SiC with high molecular weight and medium molecular weight distribution was synthesized from polydimethylsilane at normal pressure. The chemical formula, the number average molecular weight, and the polydispersivity index of the synthesized PCS are SiC1.94H5.01O0.028, 1135, and 1.66, respectively, which can be attributed to the higher reaction temperature used for polymerization. The polymer to ceramic conversion of PCS was completed at 900 °C with a ceramic yield of 85%. The crystallization started at 1100 °C, and at 1200 °C, well resolved peaks of β-SiC were formed with small amount of α-cristobalite. The X-ray diffraction (XRD) and transmission electron microscopy (TEM) studies indicated the presence of nanocrystalline β-SiC. © 2015, The Author(s).