Abstract: A in-service trenchless repair method for disconnection of a drainage pipe includes steps of: detecting the disconnection by a pipe sonar, and making a traction rope; pulling a hollowed cylindrical airbag to the disconnection according to the mark on the traction rope; controlling an airbag valve by an air compressor on the ground to inflate the hollowed cylindrical airbag, so that the hollowed cylindrical airbag is in close contact with pipeline wall after inflation; drilling a grouting hole on the ground surface directly above and on both sides of the disconnection until reaching the disconnection, and inserting a grouting pipe into the grouting hole; then injecting a double-slurry quick-curing repair material into the disconnection through a grouting system on the ground and waiting for curing; deflating the hollowed cylindrical airbag and pulling out by the traction rope.