We present a computational method for the ab-initio study of the magneto-optical quantities using the augmented plane wave plus local orbitals (APW+lo) method. The calculations are performed within the local-density (LDA) approximation. In the present paper, the optical conductivity is the basic quantity for the evaluation of the magneto-optical Kerr effect (MOKE). Thus it is well described and calculated. Considerable work has been performed on the magneto-optical Kerr effect using experiments, however, no experimental or theoretical work has been investigated on rare-earth silicide ErSi2, in particular using ab-initio method. Our results consist a prediction. (C) 2008 Elsevier B.V. All rights reserved.