The present invention provides a wavelength division multiplexer and a packaging method, including a first, second graded refractive index lens, a filter coating, a first, second, third UV adhesive layer, a first, second A wave splitting unit of an optical fiber guide, and an outer tube unit having a tube wall, an accommodating space, and two closures, and the lenses respectively have a first, two end faces, a first outer peripheral surface, and a third, Four end faces, a second outer peripheral surface, the filter coating is coated on one of the first and third end faces, and the optical fiber guides respectively have a fifth and sixth end faces, a third outer peripheral face, at least one optical fiber, and a seventh and eighth end faces, a fourth outer peripheral surface, and at least one optical fiber, the UV adhesive layers are respectively coated on the first and second outer peripheral surfaces adjacent to the first and third end faces, the second The positions of the first and third outer peripheral surfaces adjacent to the second and fifth end surfaces, and the positions of the second and fourth outer peripheral surfaces adjacent to the fourth and seventh end surfaces.