Abstract: Using deionized-water as working fluid, the large hight-to-width rate micro-fin cooling systems are proposed. The heat transfer characteristics of these micro-fin cooling systems are experimentally studied. It is found that the heat dissipation could reach 2.83106 W/m2 at the flow of 57.225 L/h and the surface temperature of 73.4 ℃, and the heat sink can meet the demand of high power heat dissipation requirements. When the bottom temperature is fixed, the heat dissipation increases with the rise of flow and finally trends to a constant. The Nusselt number increases with the increase of Reynolds number. The heat transfer performance of the present sink is over predicted by the previous correlations. Therefore, new correlation is proposed to evaluate heat transfer performance of micro-fins with consideration of the Nusselt number as a function of the Reyonolds number and Prandtl number. Key words: micro-fin;heat transfer;heat radiator;high heat flux