By using the high frequency saturation filtering effect and dynamic carrier recovery time, the dependence of the frequency chirping and intersymbol interference (ISI) of a wavelength converter based on cross-phase modulation in Mach-Zehnder wavelength converter is analyzed. While the extinction ratio is kept the same at different probe power for out-phase converting, the poorer performance of the converted signal is due to a longer gain recovery time and the larger intersymbol interference. But for in-phase converting, the high probe or fast carrier recovery time is not surely better than that of low probe power.