We investigate a radiation-shaped heat sink (RHS) using equivalent thermal resistance model, working temperature measurement and software simulation. The thermal resistance model is based on principles of heat transfer. Two digital thermometers and the Icepak software are utilized to conduct temperature measurement and thermal simulation, respectively. The results of the measurement and simulation agree with each other, proving the feasibility and reliability of using Icepak to carry out thermal analysis. In order to decrease the working temperature of the heat sink, controlling variable method is adopted to optimize the number of its fins and the aluminium plate′s diameter and thickness by Icepak, which can serve as a reference for the structure optimization of the RHS.