The invention relates to a preparation method of titanium dioxide, and discloses a preparation method of titanium dioxide according to a chlorination method. The preparation method is mainly characterized in that chlorine gas separated from a filter is cooled by a cooler, and then compressed by a chlorine compressor, the compressed low-temperature chlorine gas is returned to a cooling pipe through a connecting pipe, and is mixed with a mixture, obtained through oxidation reaction, in the cooling pipe, so as to cool the mixture, obtained through oxidation reaction, in the cooling pipe. The preparation method has the advantages that 1) the temperature of the mixture obtained after the oxidation reaction is rapidly reduced; 2) no new impurity is introduced into the mixture obtained through oxidation reaction; 3) the produced titanium dioxide is good in particle dispersity, uniform in particle size, and applicable to high-quality pigment preparation.