Products of slow thermal decomposition and fast therlnal explosion of α-Pb（N₃）₂ were detected by a time-flight mass spectrometer.Different mechanisms of these two reactions vvere determined.In slow thermal decomposition of -Pb（N₃）₂ ,the first step is excitation of ther π-electron in azide ion to form an azide radical.Then nitrogen gas is formed through bimolecular decomposition of azide radicals,which is the ratecontrolling step in the whole process.In thermal explosion of α-Pb(N₃)₂ products are nitrogen atom and nitrogen molecule.Formed from simultaneous breakdown fo π-and ó boud in-N₃,because of the high energy released in the reaction system.