Abstract: In order to suppress the self-interference and improve spectrum efficiency in full duplex massive multiple input multiple output (MIMO) network, an optimal antenna allocation algorithm is proposed. In the full duplex system, the base station exploits zero-forcing linear processing and therefor has imperfect channel estimation. A tight lower bound on the sum-rate for the system with large number of antennas is derived. By resorting to the tight lower bound, a sum-rate maximization problem in terms of antenna ratio is formulated. The analysis and simulation results show that, 1) the ratio of receive antennas and transmit antennas is proportional to the training power of uplink, while it is inverse proportional to the training power of downlink; 2) the optimal antenna ratio converges to 1, when the total number of antenna goes to infinity.