The DOS, COOP and O 1s binding energy are calculated for Ni24(100) model surface with oxygen adsorbed on it. The calculation is made with PC/386 using the program obtained by converting EHMACC(VAX version) into PC version. The calculation shows the dissociative adsorption of oxygen molecule, of which the main cause is attributed to the transfer of the $d{pi}$ and $d{delta}$ electrons of Ni to the antibonding $1{pi}_g$ of oxygen molecule. The O ls shift on the adsorption is calculated using the valence potential method, and the results agree fairly good with the experimental values.