The invention discloses an external wall reserved hole filling device. According to the main points of the technical scheme, the device comprises a cylinder, one side of the cylinder is provided withan outlet, the cylinder is internally and slidingly connected with adaptive plugs and provided with a push shaft for pushing the plugs, the top of the cylinder is provided with a discharging opening which is connected with a material storage groove and movably connected with a baffle, and the push shaft is provided with a linkage piece which drives the baffle to be opened through linkage when thepush shaft is retracted back; through the arrangement above, more plugs can be placed in the material storage groove, after the push shaft is pushed to make the plugs in the cylinder plug external wall reserved holes, the baffle can be opened through the linkage after the push shaft is retracted back so that the next plug in the material storage groove can enter the cylinder, then the push shaft is pushed forwards to plug the external wall reserved holes, in this way, multiple reserved holes are plugged through repeated operation without loading the plugs into the cylinder one by one in the plugging process, and therefore the device is more convenient to operate and high in efficiency.