Abstract: In those programs thus far designed, the transfer function of the error channel used to be regarded as 1. This approach is found to be unreasonable, and the paper discusses in particular the online adaptive modeling of the error channel in AANC (adaptive acitve noise control) in partial space. It is found that, with this the online adaptive modeling of error channel, the stability of the system is improved, and the attenuation level is increased. In the paper is given the theory, its implementation and the program design for online adaptive modeling.