The present invention relates to a green technology to produce chlorinated rubber without using carbon tetrachloride and water by using 1,1,2-trichloroethane as the solvent and iodine as the catalyst. The natural rubber reacts with an excessive amount of gaseous chlorine at 60-100° C. for 3-8 hours and the product is then dried. The method of the present invention complies with the environmental requirements of “The Montreal Protocol on Substances that Deplete the Ozone Layer” by abandoning the usage of CCl4. It also complies with the relevant regulations regarding ship-shell paints. Moreover, it is easy to carry out and is suitable for industrialization.