The present review describes chemical modification of natural rubber, consisting of cis-1,4-polyisoprene, to introduce functional group. Natural rubber was first purified with urea in latex stage to remove proteins which inhibit precision control of the chemical modification. The resulting purified natural rubber was subjected to radical and ionic chemical reaction. Introduction of hydroxyl group, carbonyl group or functional polymer at allylic position of cis-1,4 isoprene unit was achieved with radical initiator to prepare liquid natural rubber and graft-copolymer, while it was reacted with hydrogen, peroxycarboxylic acid, carbon dioxide, water and polylactide to introduce hydrogen, epoxide, carbonate, hydroxy group and tetrahydrofuran, and ester at olefinic position, respectively.
