Abstract: For the problem of short communication distance in the low-frequency magnetic communication system, a passive transponder is designed based on magnetic coupling induction. The design consists of antennas, power storage, signal processing and signal amplifier. The system adopts the idea of low-power circuits and high-power emission design, magnetic energy is converted into AC electric by the receiving antenna. Rectifier and filter circuit converts AC power into DC power. The system is supplied by DC power after a step-down by voltage circuit. Modulation signal is amplified by the signal processing module. The amplified signal is sent to the reader through the transmitting antenna. Because of the high amplifier power, the reader can easily receive the remote signal.