For the problem of classification for jamming signal in the normal communication channel, a new modulation identification method is proposed. With the help of JADE algorithm, the jamming signal is separated from the normal communication signal. Four new features is extracted from the jamming signal power spectrum and used for modulation identification. The method is robust in the presence of carrier offsets. For 2ASK, 2FSK, 4FSK, BPSK and QPSK, the algorithm is simulated under several received conditions. Simulation results show the validity of the proposed method for jamming signals with different spectrum.