In this paper, we propose and analyze a new TDMA-based cooperative MAC scheme for the two-way two-hop relay network in which there are several helpers besides a default relay node. The proposed scheme is based on the TDMA-based cooperative relaying MAC (CR-TDMA), which is designed for one-way relay networks, and thus is named as two-way CR-TDMA (TW-CR). As the main contribution of this paper, we derive the throughput performance of the proposed scheme given the relay buffer being infinity. Simulation results verify the validness of the performance analysis.