Provided are an adjustable laser wavelength alignment method and device, and a related apparatus and system. When transmitting an optical signal to a first wavelength channel of a wavelength division multiplexer, an adjustable laser can adjust a wavelength control parameter configured to control a wavelength of the optical signal transmitted by the adjustable laser, receive an optical time-domain reflectometer (OTDR) graph generated according to a reflected signal returned by the wavelength division multiplexer, and determine, according to the received OTDR graph, a value of the wavelength control parameter allowing the wavelength of the optical signal transmitted by the adjustable laser to align with that of the first wavelength channel to be wavelength configuration information to perform self-configuration, namely automatic wavelength alignment being realized via the OTDR graph when the adjustable laser is in use. Therefore, an adjustable laser in an ONU does not require a long period of testing time before leaving a factory, thereby increasing a production efficiency of the adjustable laser.