In this paper, we consider the two-way relay network (TWRN) in the presence of an eavesdropper, and construct a noisy amplify-and-forward (AF) algorithm to enhance the physical (PHY) layer security capacity. All the source nodes, the relay and the eavesdropper are equipped with multiple antennas. In the proposed noisy AF scheme, the relay first receives signals from both source nodes, adds weighted artificial noise (AN), and then amplifies and forwards the modified signal to both source nodes. In this scenario, we analyze the effects of AN and the number of relay antennas on the secrecy sum rate for different conditioning channel matrices. It is shown that AN will result in an increased secrecy sum rate, and the channel condition is a key parameter of the system in deciding the sum secrecy rate. Finally, simulation results demonstrate the validity of proposed studies.