Abstract: Radiation effect on the morphology of melt-crystallized polyethylene is studied with infrared spec-troscopy, laser light Raman longitudinal acoustic mode (LAM) spectr'oscopy, light scattering, wide angle X-ray diffraction and differential scanning calorimetry. The intensity of the band 730cm from C-H bending vibration in crystalline phase is found to decrease with radiation dose. The position of LAM peak does not change with radiation dose, but its intensity decreases. It indicates that the damage or amorpho-tization takes place-within crystalline lamellae rather on their surface. After radiation-crosslinking of polyethylene, its four clover-leaf Hv light scattering pattern keeps its pattern after melting, though its intensity decreases. The residue of the intensity after melting increases with radiation dose. From the depression of melting point with radiation dose, the G value of damage of the units in crystalline region is estimated to be 3. 5.