Heavy oil, as one of the world's hydrocarbon resources, has special characteristics that differentiate it from other instances of oil in the world. Density and viscosity of this oil result in different kind of extraction from other lighter naphtha. Normally this type of oil is immobile. So that in some parts of Canada, where the oil is spread on the surface of the earth, surface drilling machines are used transfer to it to downstream processes. The mobility of the subsurface oil must be increase in order to be extracted. In-situ combustion method is the most important method to extract the heavy oil fields. In this method, some amounts of have oil in the reservoir is burned to increase the temperature of the remained oil. So the viscosity and gravity of the oil are decreased in the way that the mobility is increased. To determine the optimized condition in the in-situ combustion process, it is essential to have synthetic parameters of this reaction such as activation energy, pre _exponential factor and the reaction mechanism as an approximate. Accordingly, various techniques have been proposed. In practice, different reactions occur when burning a fuel mixture which are generally not possible to predict. But it is not too far-fetched to introduce a good way to specify the behavior of the burning. Kissinger method, as a subset of integral method, is widely used in the literature. It is generally used to predict the activation energy of the reaction. However, in this method, it is assumed that the temperature varies linearly with time. While this assumption is valid for gravimetery analyzers, it is not more valid for real systems. In a burning reaction, there may be some exothermic or endothermic reaction which may slant the temperature from the pre estimated temperature. Here we proposed a new method based on the Kissinger method in which the so called assumption was ignored. In this study, the results of new method was compared with those of Kissinger and Vyazokin methods. It was shown that the new method could predict the activation energy extracted from Vyazokin method with a good accuracy. While the Vyazokin method is based on a trail and error procedure, the new method can predict the activation energy explicitly. Master plot method was also used to predict the pre_exponential factor. Eighteen different reaction models were used to enhance the accuracy. Use of CMG simulator and the so described synthetic parameters, a combustion tube was simulated. The mechanism of the reaction was extracted from the literature. The heat of the reactions were estimated to have the best accuracy between the simulated temperature profile and those of experimental data. Key Words: Activation energy, kinetic, modeling, in-situ combustion, heavy oil, combustion tube, Kissinger, Vyazokin