This paper showed the a numerical analysis of the thermal and fluid flow in solar concentration absorber with tilt angle, and the purpose of this study is to obtain the optimum tilt angle of the absorber. The boundary conditions of a numerical model were assumed as flows : (1) The heat source is located at the center of absorber (3) The bottom wall is opened and adiabatic. (3) The top, right and left walls are cooled wall. The parameters for the numerical analysis are tilt angles and Rayleigh numbers i.e., tilt angle $ heta=0^{circ},;15^{circ},;30^{circ},;45^{circ},;60^{circ},;75^{circ},;90^{circ}$ and 101 $leq$ Ra $leq$ 103. The velocity vectors and isotherms were dense at wall side and the heat source. The mean Nusselt number had a maximum value at $ heta=0^{circ}$ and showed a low value as the tilt angles were increased. Finally, the decrease rate of mean Nusselt number was appeared small with tilt angle when Rayleigh numbers were increased.