Abstract: To effectively identify the radio equipment and quickly ascertain the radio interference, this paper presents a spectrum watermark embedding and extracting method based on the correlation identifier. The correlation identifier that identified the embedding location of spectrum watermark was firstly embedded into communication signals under the control of identifier embedded control module in the transmitting terminal. Then the spectrum watermark was embedded by quantizing the low-frequency of wavelet decomposition of the communication signal with correlation identifier. The spectrum watermark was detected by analyzing these characteristic of autocorrelation and cross-correlation of correlation identifier. And it was extracted by quantizing the low-frequency of wavelet decomposition of received signals in the receiving terminal. Theory analysis and simulation results show that the proposed method can effectively extract the spectrum watermark without harmful inference to normal demodulation of communication signals, and there is no need to demodulate the communication signal, which can effectively reduce the complexity of spectrum watermark extracting. Thus, it provides a technical support for effectively identifying and ascertaining the radio equipment.