Based on the density functional theory, the diffusion behaviors of C, N and O atoms in V metal are studied by using the first-principles calculation method. Firstly, the site occupations of C, N and O atoms in the interstitials of the bcc V lattice are discussed. The interactions of interstitial C, N and O atoms with V lattice are analyzed, and the influence of the electronic structure on the interaction is explored. The study results show that C, N and O atoms are more stable in octahedral interstice of V metal, and a relatively strong bonding interaction is formed between their 2p-electron and the 3d-electron of V metal. The diffusion barriers of C, N and O atoms are 0.89 eV, 1.26 eV and 0.98 eV, respectively. Thus, the expressions of their diffusion coefficients are obtained. Finally, the diffusion coefficients of C, N and O atoms are compared by the Arrhenius plot. Their diffusion coefficients are calculated at 500-1100 K, and the calculation results are consistent with experimental values.