The invention discloses a middle joint connecting structure of an assembled integral frame column-beam and a construction method of the middle joint connecting structure and belongs to the field of prefabricated assembled concrete structure engineering. The middle joint connecting structure is characterized by comprising reserved holes, tensioned longitudinal ribs, U-shaped rebars, a grouting and anchoring layer, roughening layers and a concrete connecting layer, and an upper row and a lower row of reserved holes are formed in a prefabricated column; on a construction site, the tensioned longitudinal ribs are penetratingly mounted and anchored in the reserved holes of the upper row on the prefabricated column, and the U-shaped rebars are penetratingly mounted and anchored in the reserved holes of the lower row on the prefabricated column. The construction method includes: producing the prefabricated column, a right prefabricated beam and a right prefabricated beam in a factory; arranging the roughening layers respectively; correspondingly binding the tensioned longitudinal ribs and the U-shaped rebars with longitudinal ribs and stirrups II on the left and right prefabricated beams respectively; casting-in-place the concrete connecting layer to realize column-beam connection. Construction is convenient, construction period is shortened, and aseismic performance is improved.