A numerical study is conducted to investigate the natural convection heat transfer in a two cases of the enclosure ,the first case in a square enclosure of aspect ratio AR=1 and the second case in a right-angle trapezoidal enclosure with aspect ratios AR=0.45 and 0.25 .The enclosure was filled with a liquid saturated porous media .The bottom wall of the cavity was heated with a sinusoidal temperature distribution θ=0.5(1-cos(2πx)) , the vertical wall was cooled at θ=0 and the other walls were adiabatic. The governing equations were solved numerically using finite element software package (FLEXPDE). Flow and heat transfer characteristics are studied for the range of Rayleigh number (100 ≤ Ra ≤ 1000). Streamlines, isotherms and Nusselt numbers were presented. The obtained results show that the heat transfer coefficient increases with increasing of Rayleigh number and aspect ratio. A comparison of the flow field and isotherm field was made with that obtained by (Yasin et al., 2008), which revealed a good agreement.