In the hybrid quantum-classical networks, how the quantum signal wavelength and classical signal wavelength are distributed determines the degree to which the quantum key distribution (QKD) performance is affected by the classical optical signal noise. Aiming at the wavelength assignment optimization scheme based on the principle that the noise is minimal, the optimization degree of QKD performance is investigated. The effects of wavelength interval and channel number on the performance of QKD are analyzed. Simulation results show that the optimization scheme can improve the key generation rate and the furthest secure transmission distance of the networks. With a given number of quantum and classical channels, the quantum key generation rate and the furthest secure transmission distance of the networks decrease with the increase of the wavelength interval. When the number of classical channels and wavelength intervals is fixed, the total key generation rate of the networks increases with the increase of quantum channel number, while the average key generation rate and the furthest secure transmission distance of each quantum channel both decrease.