As an important intermediate of hindered amine light stabilizer (HALS), 2-chloro-4,6-bis(2,2,6,6-tetramethyl-4-piperidinyloxy)-1,3,5-triazine (CDTMTZ) is also a light stabilizer and is the basis for the synthesis of other high molecular weight light stabilizers. Through experiments, the influence of solvent, material ratio, addition method, temperature, time and other factors of different reaction stages was investigated. Through the melting point and elemental analysis of the product, it is concluded that when using water as a solvent, the material is added twice under the theoretical ratio, and the temperature of the reaction stage I. is 5~8 °C and the time is 2 h; In the reaction stage II, the temperature was 80 °C and the time was 24 h, and the CDTMTZ monohydrate was obtained, and the melting point (223.8 °C~226.4 °C) and elemental analysis results were compared with the relevant literature