Abstract: The process of phosgene-recirculation system in toluene diisocynate (TDI) production is analysed and two shortcomings of the old process are found：① High hydrogen chloride concentration of phosgene will decrease the reaction’s yield and ② The phosgene in the kettle under saturated state will become a potential hazard. In order to overcome these two shortcomings, a tower is added to purify the phosgene which is supercooled before entering the kettle to ensure safety. Compared with the old process, the weight percent of hydrogen chloride in phosgene decreases from 0.3% to 0.1%, a reduction of about 66.7%. Without any increase in refrigeration, the phosgene in the kettle is kept in a super-cooled state and production safety is improved.