This article reports about the structural, electronic and magneto-optic properties of LaXPO(X = Mn, Fe, Ni) using the density functional theory (DFT) within GW, TB-mBJ, GGA and GGA + U (U = 1, 2, 3, 4 eV). The calculated ground state values such as lattice parameters, band gap, dielectric functions, absorption coefficient, refractive index, and sumrules are in favorable agreement with the previous works and the experimental data. The computed band gap for LaMnPO (up state) is 1.25 eV (experimental value is 1.3 eV) by GGA + U (U = 4 eV). These calculations predict a half-metallic character for LaFePO and LaNiPO materials. Our results show that the nature of LaMnPO compound is magnetic, and LaFePO and LaNiPO compounds are non-magnetic materials. In band structure calculations, the GGA + U (4 eV) results for LaMnPO and TB-mBJ results for LaFePO and LaNiPO are in good agreement with the experiment. (C) 2015 Elsevier B.V. All rights reserved.