Abstract: In the applications of network communication,echo cancellers with faster convergence and more robust algorithms are highly expected. PNLMS (Proportionate Normalized Least Mean Square) and PNL-MS++,which are recently proposed,are the algorithms to achieve more rapid convergence. However,PN-LMS and PNLMS++ suffer from the same problem,such as "double-talk" disturbance,as most traditional algorithms do. To tackle this problem,this paper presents a novel algorithm named OP-PNLMS (Orthogo-nality Principle-Proportionate normalized LMS). This algorithm not only converges as fast as PNLMS++,but also shows more robustness than PNLMS and PNLMS++ during double-talk or noisy background. Furthermore,OP-PNLMS outperforms PNLMS,PNLMS++,and traditional NLMS even during single-talk. Several considerations of fixed-point DSP implementation of OP-PNLMS are also discussed in the paper.