The extinction ratio performance of converted two-channel time division multiplexing output signals in all-optical WDM (wavelength division multiplexing)-OTDM (optical time division multiplexing) converter based on cross-gain modulation (XGM) in semiconductor optical amplifier (SOA) is analyzed .The effects on the extinction ratio of converted signal is studied regarding to various parameters such as the power and wavelength of two-channel WDM input pump and probe, the bit rate, the extinction ratio of the pump, the SOA bias current, cavity length, and confinement factor. Which can provide the theoretical basis for the optimization of wavelength converter and signal processing in WDM switching nodes. It is shown by numerical simulation that high pump input power and long pump wavelength enhance signal extinction ratio of corresponding channel but decrease the adjacent channel extinction ratio. High pump extinction ratio can do too, however, the increasing amplitudes of different channels are different. Meanwhile extinction ratio of converted signal can be improved with low probe power, short probe wavelength, long cavity length, high confinement factor, and large biased current. Especially extinction ratio equalization of each channel should be considered in all-optical WDM-OTDM wavelength conversion.