A method of wavelength selection and a communication apparatus is applied to fields such as optical communication, optical switching, digital central networks, microwave photonics, liquid crystal antennas, optical phased arrays, beam forming, beam scanning, laser radars, laser projection, laser televisions, holographic display, adaptive optics, laser beam shaping, laser processing, ultrafast laser pulse shaping, laser active imaging, optical tomography scanning, and retinal imaging. When port switching occurs in a WSS apparatus, only image data of a changed local image of an LCoS image is updated within each time interval that is shorter than duration of one image frame, and a driving voltage for a pixel on the LCoS display screen is refreshed based on a priority.