The invention relates to fabricated building components, and particularly discloses a prefabricated board connecting joint. The prefabricated board connecting joint comprises a first prefabricated board, a second prefabricated board, and connecting parts; a plurality of inwards-sunken first rectangular grooves are formed in the edge of the first prefabricated board, and a plurality of inwards-sunken second rectangular grooves are formed in the edge of the second prefabricated board; the first rectangular grooves and the second rectangular grooves are arranged corresponding to each other; the connecting parts are arranged in the first rectangular grooves and the second rectangular grooves in a crossing mode; and cast-in-situ concrete is arranged at the ends, connected with the first rectangular grooves, of the connecting parts as well as arranged at the ends, connected with the second rectangular grooves, of the connecting parts correspondingly. According to the prefabricated board connecting joint, the first rectangular grooves and the second rectangular grooves are reserved in standardized production of the prefabricated boards in a factory, the surfaces of the longitudinal side edges of the prefabricated boards are flush, reserved bars do not need to be reserved, and the defects that during connection of the prefabricated boards by tenons and mortises, non-standard prefabricated boards are produced, and the reserved bars need to be reserved for the prefabricated boards, and factory manufacturing and lifting transportation are inconvenient are overcome.