Abstract: Based on the principles of chemical reaction engineering，the key technology in the production of organic isocyanates - phosgenation reaction was analyzed and the reaction could be considered as a parallel-series reaction. The proper feed-in method for this kind of reaction was studied in order to get the desired conversion and selectivity. Two kinds of phosgenation reactions used in the industry – one step reaction and two-step reaction were investigated. The latter is a better method though the former method is still used in some factories. At last，several kinds of reactors used by different manufacturers were studied and recommendation was made on how to chose a proper kind of reactor in different operation conditions.