A physical-layer security enhancement scheme in analog network coding systems based on artificial noise is proposed in this paper. In broadcast phase, the Relay node selects part of antennas from its total antennas as the received reference signal, and derives the beamforming matrix and artificial noise vector from the equivalent channel fading matrix. The simulation results show that the proposed scheme outperforms classical beamforming scheme. Compared with beamforming scheme, the proposed scheme shows about 2.5dB gain in ergodic secrecy capacity when antenna number of Relay is three, and 3dB gain when the antenna number is six. Specifically, the combined selection criterion has the similar curve compared with the one-direction criterion, in which the Relay node needs antenna selection only on Alice direction.