A wavelength locking method, apparatus, and system are provided. The wavelength locking method includes modulating, by using scrambling signals with a same frequency and different phases, each one of a plurality of optical channel signals respectively; processing, by a combiner, a splitter, and a wavelength locker, the modulated optical signals, so as to acquire photoelectricity detector (PD) signals; performing phase discrimination on the PD signals to acquire wavelength information of the optical channels; determining different shift values corresponding to the different wavelength information; and adjusting wavelengths of the optical channels according to the corresponding shift values.