In this paper, we measured the interference immunity characteristics of high-speed PLC modem using Wavelet-OFDM when the narrowband conducted interference signal was injected, and also calculated them by the computer simulation using MATLAB/ Simulink. As the results, it was clear that (1) measured PHY rate at the all frequency band hardly decreased in C/I of more than −10dB, but began to decrease rapidly in C/I of less than −30dB when the interference signal was injected in the frequency band of PLC signal, (2) when C/I became −60dB, the measured PHY rate at the frequency existing the notch band were improved around 10Mbps than that at the frequency not existing the notch band, (3) when the narrowband interference wave was injected outside of PLC frequency band, the measured PHY rate did not decrease than that in each notch band, (4) calculated PHY rate at the frequency existing the notch band were improved around 10Mbps than that at the frequency not existing the notch band, when C/I became below −10dB. Therefore, it was revealed that Wavelet-OFDM PLC system had good interference immunity characteristics.