The geometrical and electronic structures for LaNi4.75Al0.25 compound have been calculated with the generalized gradient approximation(GGA)Pewdew96 of density functional and the Full-potential linearized augmented plane wave(FLAPW)method.The results indicate that the optimized cell parameters are a=b=0.5033 nm,c=0.4018 nm and a/c=1.252,and Al atom is most likely to occupy the(0.75,0.0,0.5)position in the super-cell-the equivalent position of 3g of LaNi5 mono-cell.The band structure,density of states(DOS)and charge densities for this compound are also worked out.All the theoretical results are in well agreement with the experimental data.