Nanocrystalline silicon carbide (SiC) with a diameter of 7 nm was synthesized in a high voltage electrical explosion. It has a larger lattice parameter (0.1%) than its bulk material. Synchrotron x-ray diffraction measurements of nanocrystalline SiC were carried out to 15.8 GPa. The bulk modulus was determined to be K0T =201±10 GPa, which is substantially smaller than those of bulk material and nanocrystalline with large grain sizes. It is considered to be caused by the weaker atomic bonding strength and the imperfections of the nanocrystalline SiC.