The invention provides a tool type after-added structural slab quick connecting structure and method. The tool type after-added structural slab quick connecting structure comprises a prefabricated lightweight floor slab, the reinforcements are reserved at two ends of the prefabricated lightweight floor slab, old structural slabs at two ends of a to-be-mounted location of the after-added structuralslab are welded and fixed with the reserved reinforcements at two ends of the prefabricated lightweight floor slab, the cast-in-place concrete is poured at a connecting part of the old structural slab and the prefabricated lightweight floor slab, and the pouring part is die-filled through a tool type aluminum template. The problem that the traditional after-added structural slab way is long in construction period, large in construction difficulty and incapable of turnover is solved. The connecting structure belongs to the technical field of the building structure engineering.