The thermal decomposition process of lead azide (LA) and carboxymethylcellulose lead azide (CMC-LA) was studied by dynamic vacuum stability test (DVST) method. The test data were analyzed by differential method. The reaction mechanism function and apparent activation energy of CMC-LA and LA were obtained. The influence rule of sodium carboxymethyl cellulose crystal control agent on the stability and kinetic parameters of the thermal decomposition reaction of LA was analyzed. Results show that in the non-isothermal stage, the mechanism function of the thermal decomposition reaction of LA in the temperature range from 60 ℃ to 100 ℃ is the Zhuralev-Lesokin-Tempelman equation, the apparent activation energy(E_a)is 86.53, 42.26, 39.43, 38.09 kJ·mol^-1 and 10.84 kJ·mol^-1, while thermal decomposition mechanism function of CMC-LA in the temperature range from 60 ℃ to 70 ℃ is the Avrami-Erofeev equation with E_a of 133.02 kJ·mol^-1 and 41.87 kJ·mol^-1 and thermal decomposition reaction mechanism of CMC-LA in the temperature range from 80 ℃ to 100 ℃ is the deceleration type α-t curve with E_a of 43.07, 34.34 kJ·mol^-1 and 33.46 kJ·mol^-1. Addding sodium carboxymethylcellulose changes the reaction mechanism function of LA, leading the gas production of CMC-LA smaller at 60 ℃ to 70 ℃, and with a better thermal stability.