Abstract: As a dacryagogue, 2-chlorobenzalmalononitrile (CS) is widely used in the equipment for anti-terrorism and anti-riot in many countries. Explosion and combustion are used to disperse CS to aerosol in the air, and then make it decomposed. In order to improve the utilization efficiency of CS, there is necessity to study its performance of thermal stability and thermal decomposition. In this paper, thermal weight loss and thermal effects of CS were measured by thermal analysis (TGA/DSC) technique at different heating rates. Moreover, the properties of evolved gases were analyzed in combination with fourier transform infrared spectroscopy (FTIR). The performances of thermal decomposition of CS were investigated at the temperatures ranging from 350 ℃ to 650 ℃ in thepyrolysis apparatus by gas chromatography-mass spectrometry (GC/MS). It has been found that CS begins to melt at 96 ℃, boil near 310 ℃ and initially decompose between 450 ℃ and 550 ℃. The types of product are increased with the rise of temperature. In detail, CS is decomposed to four products at 550 ℃ and the amount of products is up to ten products at 650 ℃ when the thermal decomposition deepens. According to the experimental results, the pyrotechnic mixture for tear gas munitions should not burst above 450 ℃.