A wavelength division multiplexing-passive optical network (WDM-PON) system includes a light source provider configured to wavelength-division-multiplex a laser light source of a wavelength allotted to each subscriber and optical-power-divide the multiplexed light source, a plurality of optical line terminals each configured to transmit a light source for upward signal with the power-divided light source and convert an upward optical signal into an electric signal, a plurality of optical network units each configured to convert the light source for upward signal into the upward optical signal, and a multiplexer/demultiplexer configured to separate the signal source for upward signal transmitted from the optical line termination in each subscriber or to multiplex the upward optical signal for each subscriber transmitted from the optical network unit so as to transmit the multiplexed signal into the optical line terminal.