The multichannel transmission of dual single sideband discrete multitone (Twin-SSB-DMT) signal based on all-optical wavelength conversion (AOWC) is investigated theoretically and simulated. The generation principle of the dual single sideband signal is studied theoretically, and the relationship between the converted signal and the original signal is analyzed. The dual single sideband signal, which is with the left single sideband modulated by discrete multitone-quadrature amplitude modulation (DMT-4QAM) and the right single sideband modulated by DMT-16QAM, is obtained when we set the radio-frequency signal in the push-pull modulator. High-quality converted signals of 1-8 channels are generated through the four-wave mixing of 20 Gbit·s-1 dual single-sideband signal in the semiconductor optical amplifier. The converted signal contains the original data, and the multicast transmission of high-order signal can be achieved. The simulation results show that the dual single sideband DMT signal improves the spectral efficiency and the utilization of wavelength bandwidth, reduces the cost, and improves the performance of the whole AOWC system. In addition, according to the constellation and bit error rate curves, 8-channel polarization-insensitive multicasting signals can be directly received without crosstalk, and the cost of signal to noise ratio is low, which is good for achieving the high-quality multicast system.