The adsorption of atomic nitrogen on the Ti(0001) surface and the effect of pre-adsorption hydrogen atom were studied by first-principles density functional theory approach for nitrogen coverage ranging from 0.25 to 1.00 monolayer(ML).It is found that the on-surface hcp site is the most energetically stable and that the fcc site takes the second place.In the subsurface region,nitrogen atoms prefer to adsorb at oct sites.The calculation showed that the bonding strength increases with the increase of coverage,meanwhile adsorption energy decreases with the increase of coverage.It is found that the preadsorption hydrogen atom can transform the surface electronic structure,cause the hybridization between the H-1s orbital electrons and N-2p,Ti-3d orbital electrons and lead to the increase of adsorption energy and the decrease of diffusion barrier.