In this work, the theory of the iterative linear integral isoconversional method was illustrated in detail. This method allows the dependence of the activation energy (Eα) on the conversion degree to be accurately determined in a short time. Moreover, the method can yield the term [Aαf(α)] (Aα: the frequency factor at conversion α, f(α): the reaction model). The obtained Eα and [Aαf(α)] values can be used to reconstruct the kinetic conversion data at experimental and extrapolated conditions. The suggested method was applied to the experimental data of combustion of biomass fast pyrolysis char, and the corresponding kinetic parameters were obtained.