The reaction mechanism of the ethynyl radical and CH3OH has been studied by the Density Functional Theory (OFT) using the B3LYP functional in conjunction with the 6-311 ++G( d,p) and, 6-311 ++G(3df,2p) basis sets. The potential energy surface (PES) for the C2H+CH3OH system was also established. Calculated results indicate that products of this reaction can be (CH3OCCH + H), (CH3OCC + H2), (CH4 + CCHO), (CH2CHCHO + H), (CH3 + CH2CO), (C2H4 + HCO), (CH4 + HCCO), (CH3CHCO + H) and (C2Hs + CO). However, the formation of (CH3 + CH2CO), (C2H4 + HCO ), (CH4 + HCCO) and (C2Hs + CO) is the most favorable. This study is a contribution to the understanding of the reaction mechanisms of the ethynyl radical with many small radicals and molecules in the atmosphere and combustion chemistry.