Electrical properties of unfilled and ZnO-filled epoxy polymer are investigated by temporal spectroscopy. Transient current analysis indicates that relaxation time decreases with increasing applied voltage and adding ZnO nanoparticles, due to an increase of molecular mobility. Moreover, adding ZnO nanoparticles to polymer epoxy matrix enhances the dielectric function parameter (n). This parameter gives information on the expected conduction mechanisms. In the other hand, the depolarization current was simulated to determine the equivalent circuit. We obtain an equivalent circuit consisting of 3 R-C parallel branches. We note that ZnO loading causes a fall in the capacities values, and an increase in resistances of nanocomposite. This resistive behavior can be explained by an increase of interactions and bond formation between ZnO nanoparticles and epoxy polymer chains.