Abstract: Performance is analyzed of the multiple two-way relaying systems with three-slot Time Division BroadCast (TDBC) protocol employing adaptive modulation. The end-to-end SINR of the system is presented when channel estimation error exists. Then the distribution of its upper bound is given by transforming the expression to sum of multiple variables which obey exponential distribution through inequality zooming. Upper bound of the close-form expression of average spectrum efficiency is derived employing the distribution. Simulations show that the theoretical analysis matches well with the Monte Carlo results. The average spectrum efficiency decreases when the channel estimation error increases. Error floor will emerge for the self-interference can not be totally eliminated. Whats more, the optimal power allocation strategy at relay to reduce the impact of channel estimation error is proposed.