A trenchless rehabilitation device for disconnects on large-diameter concrete drainage pipe and method thereof is provided; which includes: a pipe CCTV, a water blocking device, a lining repairing permanent structure, and a grouting device. The pipe CCTV is configured to determine the location of the pipe disconnection; the water blocking device is configured to form the working space; then the rubber seal lining short tube and multiple expanded round fixed steel plates are configured to form the inner repair permanent structure, and the grouting equipment is configured to insert the expanded round fixed steel plates. The grouting holes are configured to polymer grouting on the periphery of the pipe disconnection and the soil void. The trenchless repair process provided by the present invention can form a composite pipeline disjointed repair structure of inner repair permanent structure and polymer grouting material.