Abstract: This paper proposes a security method in the physical layer by using artificial noise and spatial modulation technique. The information is conveyed by the transmitting antenna index and amplitude-phase modulated symbol. The other antennas transmit the artificial noise located in the null space of the legitimate channel to interfere with the eavesdropper's signal detection without affecting that of the legitimate receiver. The achievable secrecy rate and bit error rate bound of both the legitimate receiver and the eavesdropper are analyzed, and the simulation is done to verify the secrecy performance of the scheme. The results show that the legitimate receiver has a much lower bit error rate than the eavesdropper, whose bit error rate is about 0.5. Thus the secrecy rate can be improved considerably.