Within the framework of pair potential approximation and shell model the we have studied the charge-ordering phenomenon in La1.5Sr0.5NiO4. The charge-ordered phase is shown to be stable. According to the results of our calculations the charge redistribution plays the main role decreasing the total energy of crystal. On the other hand the lattice distortions accompanying the charge redistribution is shown to be associated with lattice relaxation within NiO2 layers.