The mutual coupling parameter was introduced into the theoretical model of semiconductor laser wavelength conversion. Based on the improved theoretical model of wavelength conversion, the bit error rate versus mutual coupling parameter was given. The simulated results demonstrated that the mutual coupling parameter depended on the powers of signal and probe lights and the wavelength space between them. The higher the mutual coupling parameter, the less the bit error rate. It was also demonstrated that with higher signal power, lower probe power and lower wavelength space between them, which means larger mutual coupling parameter, the bit error rate of wavelength conversion is minimum, the decreasing of signal light and the increasing of probe light will increase the bit error rate.