The knowledge of the interaction of photons with matter is of vital importance to investigate fundamental nuclear physics problems. Giant dipole resonance (GDR) mechanism is dominant up to 30 MeV at photo-absorption cross-section. The photo-absorption cross-section curve against the photon energy displays one or multi-peak Lorentzian functions according to the deformation of the nucleus. Theoretical photo-absorption cross-section calculations generally focus on the estimation of GDR parameters. Theoretical reaction codes use GDR parameters to reproduce photon-induced nuclear reactions. In this study, photo-neutron cross-section calculations of Fe-54,Fe-56, Zr-90,Zr-91,Zr-92,Zr-94, Nb-93 and Ag-107 isotopes have been done with the TALYS 1.8 and EMPIRE 3.2.2 nuclear reaction codes in the GDR region. During these calculations, both codes were firstly operated by using the predefined and existing GDR parameters within the codes. Later on, a new set of GDR parameters have been obtained by running a Lorentzian model based code in where the available experimental data are also considered. Levenberg-Marquardt algorithm has been used with 10(-6) function tolerances and 400 iterations for optimization. These new obtained GDR parameters then replaced with the existing GDR parameters within the TALYS code and the photo-neutron cross-section calculations for the investigated isotopes have been repeated. Ultimately, in order to discuss the outcomes and the effects of using new GDR parameters, obtained results were analyzed by comparing them with the experimental data from the Experimental Nuclear Reaction Data (EXFOR) library.