The utility model discloses a device used for sealing and consolidating a formwork at joint seams of concrete walls. At the horizontal joint seam position of the concrete walls and a concrete slab, a full-length sealing strip is attached along the side face of the top of the concrete slab, the formwork located at the outer side of an upper wall is lengthened downward and attached to the concrete slab and the outer side of a lower wall which are located on the lower layer and have been constructed, a row of PVC casing pipes are pre-buried in the concrete in the upper portion of the lower-layer wall, a fixed threaded rod is arranged in each casing pipe, a short steel bar is welded to the tail end of each threaded rod, and the short steel bars serve for supporting at the inner sides of the concrete walls; an upper support steel tube and a lower support steel tube are arranged at the outer side of each formwork timber dorsal bar and the elevation position of the corresponding fixed threaded rod; after the front end of each fixed threaded rod passes through a panel of the formwork, a hill-shaped fastener and a nut are used for locking the corresponding support steel tubes at the elevation position. By means of the device, the rigidity and the sealing performance of the formwork are greatly improved, the general quality defects such as slurry leakage of the formwork, formwork expansion, concrete 'foot rot', honeycomb, reveal of reinforcing bars and faulting of slab ends are effectively overcome, the compacting and surface flattening of the concrete at the joint seams are guaranteed, and the device has the advantages that the structure is simple, the use is convenient, and the device can be used repetitively.