In the non-cooperation communications system, it is difficult to recognize Continuous Phase Modulation(CPM) signals. A novel method for the recognition of CPM signals is proposed to solve this problem. By combining spectrum line test, the signals instantaneous amplitude spectrum features are employed to distinguish CPM signals from Amplitude Shift Keying(ASK)，Frequency Shift Keying(FSK)，Phase Shift Keying(PSK)，Quadrature Amplitude Modulation(QAM) signals. The method obviates the requirements of preprocessing tasks like estimation of parameters and synchronization. Simulation results show that the correct classification rate of CPM signals is above 95% under 4 dB SNR. Compared with existing methods，the proposed method which has lower computational costs and higher recognition probability is easy to be implemented.