Abstract: Co is very toxic gas so separation of this gas is very important .In this study separation of co and h2 Has been studied. Prevent the emission of carbon monoxide in the environment is very important..in this study Lennaed-Jones potential was used for gas-gas and gas-carbon nanotube interactions and the potential parameters for the carbon-gas and carbon-carbon interactions were obtained from the Lorenz-Berthelot combining rules. The study has been done by using the equation state of Virial and finding the second coefficient in Virial equation. Final steps were the inside density, outside density and total density of nanotubes .My calculation.result show that this sepration is possible.