In the present report, the 3-dimensional CFD simulation of heat transfer and air flow in circular pin fin heat sink are presented for Electronic component cooling application. The circular pin fin heat sink are simulated for different alloys like Aluminium alloys i.e.6063-T83, 7075O (SS) and Copper alloys i.e. Chromium Copper. In this study comparing the heat transfer rate with respect to different alloys under Natural Convection. The goal of this study was to maximize the thermal performance of heat sink with respect to different material such that it helps to finding material selection, low cost material and good heat transfer rate for designing the heat sink. Aluminium are the materials especially used rather than brass and iron. The utilization of pins in the heat sink increases the heat transfer area to reach the extreme rate of heat loss in a restricted space.