Abstract: A new method of the multiple rates-isotemperature is proposed to define the most possible mechanism g(α) of thermal decomposition; the iterative isoconversional procedure has been employed to estimate apparent activation energy Ea; the pre-exponential factor A is obtained on the basis of Ea and g(α).By this new method, the thermal analysis kinetic triplet of dehydration of zinc oxalate dihydrate is determined, where apparent activation energy Ea is 87.22 kJ•mol－1; pre-exponential factor A is 4.2120×108～7.2328×108 s－1 and the most probable mechanism belongs to random nucleation and growth Am (Avrami-Erofeer equation) ,with integral form g(α)=[－ln(1－α)] 1/m, and differential form f(α)=m(1－α)•[－ln(1－α)](1－1/m) , accommodation factor m=1.85～2.00.

Key words: Multiple rates-isotemperature method, Isoconversional method, Non-isothemal kinetics, Zinc oxalate dihydrate, Accommodation function