Some embodiments of this application relate to the field of optical communications technologies, and provide an optical fiber junction assembly and a sealing method thereof, and an optical fiber junction box, to resolve a problem that sealing performance of an optical fiber junction box is reduced due to aging of a rubber ring. In the optical fiber junction assembly, a first housing has first matting surface and an accommodating cavity; a first welding bump is disposed on the first matting surface, and is disposed around an opening of the accommodating cavity; when a second housing is docked with the first housing, a second matting surface of the second housing is disposed opposite to the first matting surface, and covers the opening of the accommodating cavity; a second welding bump is disposed on the second mating surface; when the first housing is docked with the second housing, the second welding bump is in contact with the first welding bump; the first welding bump and the second welding bump are configured to: form colloid after being heated and melted, and connect and seal the first matting surface and the second matting surface; and an overflow groove is disposed on at least one of the first matting surface and the second matting surface, and is configured to accommodate the colloid.
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