The effect of sample mass on the kinetics of the non-isothermal mass-loss process of molten NH4NO3 was investigated by TG-DTG. The apparent Arrhenius parameters were shown to decrease with increasing sample mass. Using the conventional method of kinetic calculation, it was shown that the sample-mass-dependent variation in the apparent pre-exponential factor results from the use of fractional reaction in the kinetic expression. The value of the apparent activation energy varies consequently to compensate the sample-mass-dependent change in the apparent pre-exponential factor on the regime of the mutual dependence of the Arrhenius parameters; this is known as the kinetic compensation effect. The specific Arrhenius parameters that are independent of sample mass were obtained by using the specific pre-exponential factor that is independent of sample mass, instead of the apparent pre-exponential factor.