Natural convection heat transfer in a porous medium with partially thermally active walls is studied with lattice Boltzmann method. Convective flow heat transfer with different heating and cooling zones, porosity, Darcy number and Rayleigh number is investigated. It reveals that at Da=10^-4 a circulating flow pattern at the middle of the cavity is found, and porosity have great influence on heat transfer at large Rayleigh numbers; As Darcy number is increased to 10^-2, streamlines exhibit a flow pattern with two vortices, and porosity have great influence on heat transfer at low Rayleigh numbers. Location of partially thermally active walls has significant influence on flow pattern and heat transfer in cavity. Bottom-top with bottom heating and top cooling provides a greater heat transfer rate compared with other partial heating. It is better than fully heated wall of cavity.