Abstract: In this paper, dynamic behaviors of high temperature thermal decomposition of HTS were studied. The contents of nitrate and nitrite in HTS were detected by spectrophotometry and the kinetic parameters of thermal decomposition were obtained. The results show that decomposition of nitrate in HTS is mainly affected by temperature and the decomposition rate coefficient increases with temperature in an exponential type, which belongs to type I model reaction with the apparent activation energy (E_a) 189. 8 kJ/mol and the pre-exponential factor (A) 7. 48×10⁵s^-1. Nitrite in HTS shows more complex dynamic behaviors and the result of nitrite decomposition is affected by both temperature and nitrate decomposition reaction. The rate of decomposition reaction is about 0. 12×10^-5-0. 13×10^-5s^-1 at the temperature range from 813 K to 873 K. When the temperature increased to 893 K, the rate coefficient decreased to 0. 005 8×10^-5s^-1. The apparent activation energy of nitrate in mixed HTS is greater than that of one-component nitrate which illustrates that the high temperature thermal stability of HTS with three elements is better than one-component molten salt.