Abstract: By analysing the actual room acoustic environments,this paper presents a novel algorithm for acoustic echo cancellation,it can dynamically change the length of the adaptive filter order.This algorithm builds a nonlinear function relationship between the length and the error signal.The filter keeps a long order when the environment changes suddenly,and the length would be shorter during the steady state.A significant reduction in the computational burden can be achieved by using the new method.Theoretical analysis and computer simulation prove that the convergence and tracking properties of this algorithm is as good as the former ones.