摘要： Introduction The dead layer thickness provided by the manufacturer increases with the aging of the HPGe detector; the increase of dead layer thickness leads to the decrease in the detector’s ef?ciency, not only due to gamma rays attenuation in the dead layer but also due to the reduction of the active volume of the detector. Purpose In this work, the dead layer in?uence on HPGe detector ef?ciency was studied by Monte Carlo simulation. Materials and methods The detector model was developed using Monte Carlo N Particle (MCNP5) code for adjustment of the dead layer thickness; the adjustment was performed according to a speci?c irradiation con?guration by collimation approach using three reference point sources: 241Am (59.5 keV), 137Cs (661.6 keV) and 60Co (1173.2 keV; 1332.5 keV). Result The calculated ef?ciencies were compared to the measured intrinsic ef?ciency ones for these point sources; a good agreement between Monte Carlo and measurements results was found after the experimental validation. Conclusion The results con?rm the variation in the dead layer thickness according to aging of the detector; the average change of dead layer is in order of 1.30 ± 0.05 mm after 9 years.