In this study, numerical simulation of natural convection in a porous square cavity filled with Fe3O4-water is investigated. A magnetic source through the left wall of the cavity is also taken into account. Radial basis function based pseudo spectral (RBF-PS) method is applied. The effects of dimensionless parameters Darcy (Da), Hartmann (Ha), Rayleigh (Ra) numbers and solid volume fraction 𝝓 are presented both in terms of streamlines, isotherms and vorticity contours and average Nusselt number through the heated wall. Convective heat transfer is inhibited with the rise of Ha, and with the decrease in Da while it is enhanced with the increase in 𝝓 and Ra.