The invention provides a horizontally-structured framework system and a construction method. A steel bar truss is connected with a soffit framework through a connecting piece to form a detachable steel bar truss composite framework, and therefore the horizontally-structured framework system can bear the self weight of concrete and additional load in the construction processes independently. The form-transmission path of the horizontally-structured framework system is that the construction load is acted on the soffit framework, is transmitted to the steel bar truss through the connecting piece, is transmitted to a vertical wood pattern or a beam framework of a side wall through the steel bar truss and is finally transmitted to a floor structure. The horizontally-structured framework system is strong in overall rigidity, the horizontally-structured framework of concrete construction is provided with no support or with few supports, backing materials and work force are saved greatly, and construction efficiency is improved at the same time.