In this present study, we are elaborating the incident photon energy dependence of gold nanoparticle dose enhancement at 7mg/g concentration by using different radionuclide's such as Co-60, Pd- 103, I-125, Cs-137,Ir-192,Au-198,Yb-169 and external beam energies 40, 50, 60, 70, 80, 90, 100, 110, 120 KeV & 6-MeV X-rays. Mass energy absorption coefficient (µen/) and mass attenuation coefficients (µ/) are generated by using WinXCOM software. Kerma relative to air value was calculated and results are discussed. Our results suggest that maximum dose enhancement was found at following source 40 KeV, I-125, 50 KeV, Pd-103, 60 KeV it was 2.07, 2.017, 1.98, 1.83, 1.8 respectively. For higher energy 6 MeV X-ray DEF almost negligible it was around 1.01. © 2019 Elsevier Ltd. All rights reserved. Selection and/or Peer-review under responsibility of International Conference on Nanoscience and Nanotechnology (ICNAN'16)