Nanocrystalline porous silicon carbide (SiC) powder was prepared from various ratios with SiO2 as silicon source and carbon black as carbon source by electrospinning method and subsequent carbothermal reduction. Their microstructure, thermal stability and porosity of prepared porous silicon carbide (SiC) powder were evaluated as function of Si to C ratios in precursor. 3C/Si could not often maintain the spherical form against oxygen.carbon reaction during calcination owing to relatively low carbon content. On the other hand, the uniformed spherical forms were presented with deep wrinkles in the other prepared samples. They were believed that the wrinkled surfaces were formed by vaporization of carbonaceous gas made from carbon and oxygen. When the carbon ratio to silicon (C/Si) was 5, the β-SiC was observed without remained silica and silicon metal. Further increase in the carbon content in the precursor led to sharp and high intensity of SiC peak. Initial decomposition temperature of prepared sample was increased with decreasing C/Si ratio. We confirmed that whereas 3C/Si and 4C/Si had higher big macropore, 5C/Si and 6C/Si had much large pore volume in the range of mesopore diameter (2-50 nm) and small macropore (50-100 nm).