Fins Are Used to Increase the Rate of Heat Transfer. Generally, the Material Used For the Application of Fins Is Aluminum Alloys. In This Project the Steady State Thermal Analysis of Rectangular Fin With and Without Cavities on the Fin Surfaces By Using Ansys Workbench 14.0. the Temperature Distribution and Total Heat Transfer Rate Through the Rectangular Fin With and Without Cavities on the Fin Surfaces Was Calculated For Different Fin Materials Like Copper, Aluminum and Brass. Steady State Thermal Analysis of Rectangular Fin, and a Specified Base Temperature Condition. Considering Rectangular Fin of Different Length Conducts Heat Away from Its Base at 5000K and Transfers It to a Surrounding at 3000K Through Convection. the Convection Heat Transfer Coefficient Is 12 W/M2k.Thermal Conductivity of the Fin Material Is Specified. a Constant Temperature Condition Is Applying at the Base of the Fin Convective Boundary Conditions Are Using at the Tip of the Fin. Comparative Study Was Done Among the Fin Material Used to Find Out the Best Material Under the Conditions. Steady State Temperature Distribution Is Investigating.