NiS nanoparticales as a sensitizer is added to cubic silver bromide emulsion for the chemical sensitization. The decay curves of free photoelectrons and shallow-trapped electrons in the cubic silver bromide emulsion sensitized by NiS nanoparticales with the continuous increase of sensitization time are measured by the microwave absorption and dielectric spectrum techniques. The courses of decay of photoelectrons in the cubic silver bromide emulsion sensitized by NiS nanoparticales vis sensitization time is analyzed. The influence of electron traps in silver bromide microcrystals on the behavior of the photoelectrons' movement is discussed. The relationships between the effects of electron traps and the depth of traps with sensitization time are analyzed. By comparing the decay characteristics of the unsensitized and the sensitized samples, the optimum sensitization time under the present experimental conditions is 80 min.