The invention discloses a prefabricated beam-column node structure in a reverse-construction-method foundation pit. The prefabricated beam-column node structure comprises a steel upright in vertical arrangement and one or multiple reverse-construction beams in horizontal arrangement, a beam-column joint connected with each reverse-construction beam is arranged on each steel upright and is of a reinforced concrete structure, and each beam-column joint and the corresponding steel upright are fixedly connected to form an integral prefabricated member; a connecting face connected with the corresponding reverse-construction beam is arranged on the side face, facing each reverse-construction beam, of each beam-column joint, and shape of each connecting face is matched with one end of the corresponding reverse-construction beam. In the process of construction, after the steel upright with mounting of the beam-column joints completed in a factory is transported to a foundation pit site, pouring of plain concrete in a steel pipe and pouring of a reverse-construction floor slab are performed after on-site mounting of the upright is completed directly, and floor slab frame beam rebars are connected through connectors reserved in the beam-column joints. The advantage of prefabrication refined processing of the factory is fully utilized to ensure effectiveness of each connecting node, so that operation difficulty and construction period occupation caused by massive welding on site are avoided.