This paper repot the radiation-induced heat -shrinkable casing and membrane of polyethylene, including the describtion of their principle, apparatus, operation method, technology conditions and practical applications. Because the casings of fixed diamensions taken are separated from the sealed pipes, they can not cut off gas, and the casing diameters are uniform. Particularly, this apparatus can be applied to blow-expand the pipe larger than 10 mm diameter. Another characteristic is that the large side feeding reel may be installed outside the feeding box.