In embedded system, multimedia application is more important than before, And these products appearing more often. In addition, handholding devices are more and more popular, so these products¡¦ price is usually chip than others, and they concern more about power consumption. So in our design, we can¡¦t only focus on performance, low power and low cost are become the one of the most important factors. The main contribution of this thesis is that in MP3 multimedia application we analyzed ¡Bestimated and optimized our hardware and software to achieve low power and low cost issues. In software part, we used the skill of optimization to optimize our complied assembly codes. In hardware part, we analyzed the MP3 decode algorithm, found the critical part, and implement them with hardware to hope we can use the smallest hardware cost, to achieve highest acceleration. And we hope that through our research, we can establish a fundament about development a special application platform.