A wavelength selective switch WSS, wherein the WSS comprises an input optical fiber collimation array, a first optical switching engine, a dispersion unit, an optical path converter, a second optical switching engine, a third optical switching engine, and an output optical fiber collimation array, wherein the input optical fiber collimation array is configured to input a first beam from a first port of the input optical fiber collimation array and make the first beam incident to the first optical switching engine; the first optical switching engine is configured to perform angle deflection on the first beam on a first plane according to a first preset angle, so that the first beam is incident to the dispersion unit; the dispersion unit is configured to demultiplex, on a second plane, the first beam that is incident from the first optical switching engine, into multiple sub-wavelength beams, wherein the second plane and the first plane are orthogonal to each other; the optical path converter is configured to refract the multiple sub-wavelength beams that are obtained after the dispersion unit performs demultiplexing onto the second optical switching engine; the second optical switching engine is configured to perform, according to a second preset angle, angle deflection on the multiple sub-wavelength beams that are obtained after the dispersion unit performs demultiplexing, so that the multiple sub-wavelength beams obtained by means of demultiplexing are incident to the dispersion unit by using the optical path converter; the dispersion unit is further configured to multiplex, on the second plane, the angle-deflected multiple sub-wavelength beams that are obtained by means of demultiplexing, and make the multiplexed multiple sub-wavelength beams incident to the third optical switching engine; and the third optical switching engine is configured to perform angle deflection on the multiplexed multiple sub-wavelength beams on the first plane according to a third preset angle, and output the angle-deflected multiplexed multiple sub-wavelength beams from a second port of the output optical fiber collimation array, wherein the third optical switching engine performing angle deflection on the multiplexed multiple sub-wavelength beams is implemented by controlling a voltage of the third optical switching engine. the input optical fiber collimation array is configured to input a first beam from a first port of the input optical fiber collimation array and make the first beam incident to the first optical switching engine; the first optical switching engine is configured to perform angle deflection on the first beam on a first plane according to a first preset angle, so that the first beam is incident to the dispersion unit; the dispersion unit is configured to demultiplex, on a second plane, the first beam that is incident from the first optical switching engine, into multiple sub-wavelength beams, wherein the second plane and the first plane are orthogonal to each other; the optical path converter is configured to refract the multiple sub-wavelength beams that are obtained after the dispersion unit performs demultiplexing onto the second optical switching engine; the second optical switching engine is configured to perform, according to a second preset angle, angle deflection on the multiple sub-wavelength beams that are obtained after the dispersion unit performs demultiplexing, so that the multiple sub-wavelength beams obtained by means of demultiplexing are incident to the dispersion unit by using the optical path converter; the dispersion unit is further configured to multiplex, on the second plane, the angle-deflected multiple sub-wavelength beams that are obtained by means of demultiplexing, and make the multiplexed multiple sub-wavelength beams incident to the third optical switching engine; and the third optical switching engine is configured to perform angle deflection on the multiplexed multiple sub-wavelength beams on the first plane according to a third preset angle, and output the angle-deflected multiplexed multiple sub-wavelength beams from a second port of the output optical fiber collimation array, wherein the third optical switching engine performing angle deflection on the multiplexed multiple sub-wavelength beams is implemented by controlling a voltage of the third optical switching engine.