In-body wireless communication has attracted increasing attention because it can not only be used in medical application but also be combined with wireless communication to replace the existing connectivity in biological telemetry monitoring [1]. Therefore, it is possible to integrate radio frequency identification (RFID) system into a brand-new device [2]. However, it has been very difficult to combine them due to high lossy of human body. In this paper, an implantable tag antenna which is designed to match an integrated circuit (IC) chip of 9.3 − j55.2 Ω [3] is proposed and realized in experiment. The dimensions of proposed antenna is 15.75 mm × 4 mm. The impedance characteristic of proposed antenna is analyzed by finite-difference timedomain (FDTD) method. By introducing the three-layered phantom, the measurements of impedance characteristic is implemented; moreover, the maximum read range of 1.3 cm is confirmed by a handy reader.