The formation of cubic SiC（B1cubic SiC） and its effect on the mechanical properties of TiN/SiC nanomultilayers were studied in this work. The results show that in TiN/SiC mulytilayer, SiC exists as a cubic structure and forms coherent epitaxially grown columnar crystal superlattice with TiN when the thickness of SiC layer is about 06nm. Multilayers show the superhardness effect with the enhancement of hardness and elastic modulus, and the highest hardness excess 60GPa. With the increase of SiC layer thickness, B1SiC transforms into amorphous phase and impedes the coherent epitaxial growth of multilayers. Multilayers present layer structure character composed of TiN nanocrystal and amorphous SiC. Correspondingly, the hardness and elastic modulus of multilayers decrease. The formation of cubic SiC and coherent growth structure of cubic SiC and TiN appear to be likely the origin of the superhardness effect of TiN/SiC nano-multilayers.