With the development of manufacture technology, it is a critical problem for the reliability of avionic devices that components have to operate at high heat flux. It is essential to add heat sink on the top of power components. This paper presents the use of Taguchi method in optimizing the heat sink. At first, several parameters of the heat sink are chosen to be controllable factors. The machining errors are the uncontrollable factors. Then, four orthogonal arrays are used to lead the design of experiments (DOE). Basing on the results, the optimal design of heat sink can be chosen. Additionally, the reliability of componente can be improved by using this method.