Thermal behavior of poly 5-vinyltetrazole was studied by thermogravimetry-derivative themogravimetry (TG-DTG). The specific heat capacity of poly 5-vinyltetrazole was determined by the micro-thermal method and theoretical calculation. The results show that the thermal decomposition reaction kinetic equation of the second (main) decomposition stage is: dα.-dt=10^21.03.-β 3.-2(1-α)×［-ln(1-α)］^1/3exp(-2.292×10⁵/RT), the critical temperature of thermal explosion is 588.63 K, the adiabatic time-to-explosion of poly 5-vinyltetrazole was calculated to be 251.4 s.