The invention discloses a dynamic multicast downlink data transmitter modulated by a single side band subcarrier, belonging to the technical field of optical communication. The dynamic multicast downlink data transmitter modulated by a single side band subcarrier comprises a plurality of single-wavelength channel devices, an array waveguide raster, a comb filter, an intensity modulator and a multicast data generator, wherein the single-wavelength channel device is connected with a branching port of the array waveguide raster for transmitting downlink wavelength-division information; a combining port of the array waveguide raster is connected with an input port of the comb filter for transmitting downlink wavelength-division multiplexing information; an output port of the comb filter outputs downlink unicast wavelength-division multiplexing signals; the other output port of the comb filter is connected with the intensity modulator for transmitting downlink single side band subcarrier wavelength-division multiplexing signals; the multicast data generator is connected with the intensity modulator for transmitting multicast data information; and the intensity modulator outputs modulated downlink single side band subcarrier multicast wave-division multiplexing signals. The invention is applied to long-distance dense wavelength-division multiplexing passive optical networks needed to support dynamic multicast service.