The invention discloses a large-span roof displacement unloading construction method which is applicable to large-span roofs of large exhibition halls like workshops, museums and gymnasiums. The large-span roof displacement unloading construction method mainly utilizes a supporting and jacking method to perform supporting and jacking under nodes of a lower chord of a roof truss to perform unloading on the roof truss, so that deformation and descending of the roof truss are prevented, steel materials and labor are saved, and the large-span roof displacement unload construction method is easy and convenient to operate and suitable for being widely used.