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Most of reactions in the metallurgy are heterogeneous that have a complicated mechanism, for which the kinetic treatment is complex. In general, one has to find the controlling step first, and based on which to derive the corresponding kinetic formula to describe the kinetic behavior. Currently, the most popular method to determine the controlling step is so called the Sharp method, that is, deriving a series of formulae based on different assumed controlling steps in a consecutive heterogeneous reaction, then comparing the experimental data with various kinds of formulae to decide which formula can meet the experiment data well, and from which to select the most suitable controlling step. Nevertheless, because all these formulae used in estimating the controlling step involve some unknown parameters, for instance, the Jander equation, Gingstling-Brounshtein equation, parabolic equation… etc. all involve an unknown parameter “k”, that will prevent us from obtaining an accurate activation energy. In this article, we will give a new method based on our series of new formulae concerning the kinetics of multiphase reactions, in which all parameters contained have clear physical meanings, therefore, when they have been used to fit the experimental data, one can obtain a more accurate activation energy and the least relative errors. Some examples have been presented to show the advantages of this new method.