Abstract:In this paper, a new adaptive filtering algorithm is proposed based on the anal-ysis of the orthogonal projection of gradient vectors described in Lim(2000). In the new algorithm, a time-variant forgetting factor is introduced to estimate the Mean Square Er-ror(MSB) and change the updating direction of adaptive filter coefficient vector. Further-more, the new algorithm is extended to two-channel algorithm for multi-channel acoustic echo cancellation. Simulation in MATLAB shows that the new algorithm has good conver-gence and tracking capability to time-variant and time-invariant system, and can overcome the weakness in convergence and divergence of the Lim’s algorithm(2000). Moreover, the extended algorithm is of less computation, faster convergence, and higher accuracy when applied in multi-channel acoustic echo cancellation. Its convergent speed and accuracy are better than that of the algorithms proposed by Benesty(1996) and Sankaran(1999).