2,2′-Azobis[2-(2-imidazolin-2-yl) propane] dihydrochloride (AIBI) is a class of initiators that share water-soluble features, which was widely employed in the chemical polymerization industry. The merits of AIBI are that it can conduct smooth, stable, and controllable decomposition reaction and initiate polymerization efficiently at low temperature and concentration. Unfortunately, due to the high formation enthalpy and through a large amount of gas release, AIBI has high-potential thermal hazards. Therefore, the thermal behavior of the whole decomposition process is analyzed through series of simultaneous thermogravimetric analyzer and differential scanning calorimetry tests coupled with the advanced thermal investigation. It is found that AIBI would rapidly decompose and abruptly release an enormous amount of heat in the range of 170 to 180 °C, but with only 10% mass loss in this period. These thermal parameters can be used to describe the thermal stability of AIBI, thus effectively preventing the thermal hazard and loss of control of AIBI in the process of production, transportation, and storage.