A PLC-based wavelength-tunable WDM-PON system with an optical wavelength alignment function, the WDM-PON system comprises: a PLC platform formed on a silicon substrate; a semiconductor chip comprising an active region generating light and a passive region located in front of the active region for vertically coupling the light generated in the active region; a planar lightwave circuit (PLC) waveguide; one portion of a PLC platform where the semiconductor chip is surface mounted; waveguide Bragg grating (WBG) formed at a predetermined location of the PLC waveguide; a directional coupler transferring an optical power by permitting the passive region to approach the PLC waveguide; a heater terminal, which is formed on the WBG; and a V-groove for attaching an optical fiber to another end of the PLC waveguide. Accordingly, a WDM-PON system having a function of realizing a cost-effective optical wavelength alignment can be provided.