This paper considers an amplify-and-forward two-way relay system with frequency selective fading channels. The knowledge of channel state information is assumed not available for all nodes. An efcient transmission and signaling scheme is proposed to identify the transmitted symbols and multi-tap channel coefcients using the M-ary phase shift keying transmitted symbols. A blind receiver is derived using the least square error criterion. Simulation results demonstrate that the proposed transmission and signaling scheme outperforms an existing conventional training scheme where pilots are applied to estimate the channel coefcients.