In this research, we investigate the interaction of HCN gas with SiCNTs to making new absorber and sensor for HCN gas. All stable adsorption structures are individually optimized by using density function theory at the cam-B3LYP level of theory using the Gaussian 09 set of programs. From optimized structures the DOS plots, MEP plot and quantum molecular descriptors: gap energy, chemical potential (μ), global hardness (η), electrophilicity index (ω), and electronegativity (χ) of the nanotubes are calculated. The results indicate that the adsorption of HCN from N and H head in the vertical direction of surface of SiCNTs is favorable than other those models in thermodynamically approach. The quantum parameters demonstrate that the SiCNTs is a good candidate for detecting HCN gas.