The invention relates to a manufacturing technology of a soft polyurethane composite waterproof sound-absorbing membrane. The technology is simple and can well guarantee the product quality of the polyurethane composite waterproof sound-absorbing membrane, the binding force between various layers of the polyurethane composite waterproof membrane is very strong, the heat-preserving effect and the waterproof effect are good, membrane pasting adhesion is compact, and the surface is smooth and clean.