Nitroguanidine (NQ) is usually suggested add water as stabilizer before transport and storage. To investigate the thermal decomposition characteristic of the mixture, differential scanning calorimetry (DSC) was used to test the thermal decomposition behaviors of NQ under dynamic and isothermal conditions. The specific heat generation of the decomposition reaction were about 311 and 305 J·g^-1 for dynamic and isothermal DSC. The activation energy of NQ solution under dynamic DSC (E_α=84-78 kJ·mol^-1) and isothermal DSC (E_α=86-78 kJ·mol^-1) obtained by Friedman method was very close, and the value of it did not show much variation; indicated the reaction could be expressed as single step mechanism. And the bell-shaped curves under isothermal DSC indicated the autocatalytic character of it. Then a more accurate autocatalytic model was chosen to describe it, nonlinear fitting was used to calculate the kinetic parameters, the model function equation was expressed as dα/dt=exp (18.03) exp (-92170/RT)(1-α)^1.111 +exp (18.00) exp (-76400/RT)(1-α)^1.111α^1.995. And the dynamic data well fitted with the model curves, verified the correctness of the single autocatalytic model.