Abstract: In this paper, a 16QAM in BC of HFC is studied, and the effects of noise and channel characteristic on QAM are analyzed. A scheme of improving the quality of QAM by adopting adaptive equalizer is put forward, which is fulfilled with CPLD devices. The technology can improve the credibility of the equalizer and reduce the period of design. At present, the datum about the technology of the equalization of complex signal is very less, while the complex of equalizer can be apply to the system of communication. So it is a feasible technology method.