Severe noise and interference on the upstream channel in the HFC system and noise funneling effects are very hard. These noise and interference abstract as narrow band interference and take a nonlinear suppression measure from the point of signal processing. High efficient nonlinear suppression arithmetic MLMS/MRLS/MFTF can be applied in the narrow band interference suppression. The SNR improvement of QPSK is better than 16QAM when they are interfered by several kinds of frequency. The error sign rate of QPSK is lower than the 16QAM too. In this way, the anti-interference capability of QPSK is a little better than 16QAM under the same input SNR, but the difference can be shorten by narrow band interference suppression.