The utility model relates to a thermal shrinkage device of thermal shrinkage cap used on the bottleneck of steam heating packing bottle. The thermal shrinkage device is composed of a vapor generator, a vapor clarifying and an overheating device a vapor-water separator, a positioning device, a vapor distributor, a shrinking device for the thermal shrinkage cap. The utility model is a key equipment used in the thermal shrinkage package of the thermal shrinkage cap in packing alcohol, beverage, dressings, medicines and so on. By modifying the key structural design of the thermal shrinkage device of thermal shrinkage cap and replacing the electrical heating with direct vapor heating, the thermal efficiency of the equipment is improved and the manufacturing cost of the equipment is reduced. The utility model enables the shrunk thermal shrinkage cap keep its quality and color and never burst or give air bubble and have good flexibility and smooth appearance; also the manufacturing cost of the equipment is reduced considerably and the thermal efficiency and production efficiency is improved.