Due to the fast growing in multimdea industry in recent years, it has brought to produce various kinds of multimedia products. Most of these products are small-sized and portable devices which are built in Li-Polymer batteries for easy to carry and listen wherever and whenever the users go. This thesis is for the research on sound expansion & performance improvement on the basis of small sized FM transmitted wireless handsfree to mobile phone. It's not good for the indivisual to use FM frequency which is not allocated to the individual, because of limited output power, so, it causes to decline the performance. To improve it, PCB pattern antenna is used and it's connected to antenna Feeding part. Thus, it has brought to suppress noise and resulted in good performance of output power. After that, it is applied to mobile phone, and this paper approaches to control mic gain for increasing call reception and to fulfill the advantages of sound expansion by wireless FM transmitting. And, it's the verification and whole test for eliminating echo.