This paper reports the radiation crosslinking reaction of three-component ethylene-propylene copolymer (EPDM). The reaction taking place in random at high dose range obeyes Charlesby-Pinner equation and Chen-Liu-Tang equation. At low dose range radiation crosslinking of EPDM is enhanced due to the presence of third monomer (bis-(cyclopentadiene)) which accelerates the reaction with its double bond. The radiation crosslirking reaction is also accelerated by the addition of MI. The radiation crosslinked EPDM containing 50-70% gel was obtained with the addition of 1% MI in 2-4 Mrad dose range.,The structures and properties of the radiation crosslinked EPDM were measured. The mechanical property and thermal property had been improved. The tg δ maintains in the order of 10,-3,.,It is expected that the radiation crosslinked EPDM may be a promising material for making insulated wire, cable and heat shrinkable tubing.