In this paper, natural convection of Cu-Water nanofluid inside an enclosure which is partially filled with porous media, with internal heat generation has been studied numerically. Cu-water nanofluid was used where Maxwell and Brinkmen models determine its properties. Due to the low velocity of nanofluid, Darcy-Brinkman equation used for the modeling of porous media. In order to gain the maximum energy from the temperature dependent heat source, different parameters such as Rayleigh number, volume fraction of nanoparticles, porosity of porous matrix and heat conduction ratio has been investigated. The results show that increasing the volume fraction of nanofluid increases Nusselt number at all porosities and Nusselt will further increases at lower porosities. Changes of thermal conductivity ratio were effective only at low porosities and causes to fast conduction of generated heat and two-fold increase in Nusselt number. Moreover the porosity changes at different thermal conductivity ratio Cause to minimum Nusselt at the porosity of 0.4 to 0.6. Increasing Rayleigh number will lead to nanofluid penetration increase into the porous matrix and with further matrix cooling more increase in Nusselt number in all porosity ranges will be achieved.