The invention relates to a chlorination method and chlorination device in a chloropropene production process. The method comprises the following steps: liquid chlorine is gasified by a chlorine evaporator, enters a chlorine buffer tank, and enters a mixing section of a chlorination reactor; propylene is condensed and gasified, and sent into the mixing section of the chlorination reactor, wherein the mole ratio of the propylene to the chlorine is (4-6):1; and the propylene and chlorine are mixed and perform chlorination reaction in the chlorination reactor. The invention also relates to a chlorination device for chlorination reaction. The method solves the problem that the yield of the chlorination reaction can be influenced by the fluctuation of reaction temperature due to fluctuation of any of propylene pressure, propylene flow rate, chlorine pressure chlorine flow rate, condensing tower pressure, propylene/chlorine ratio and the like, and has the advantages of stable chlorination reaction temperature and high chlorination reaction yield.