There are various methods for determining the reaction parameters using thermal analysis data. In recent years, genetic algorithms have been considered as a new method for the determination of kinetic parameters. In the present study, calcination kinetics of ulexite was investigated by thermogravimetry (TG) using the Coats-Redfern and genetic algorithm methods. The parameters of reaction (activation energy, frequency factor, and order of reaction) and their relative standard deviations were calculated by the Coats-Redfern and genetic algorithm methods. Also, the results obtained from both methods were compared. For the second region of the dehydration process, the Coats-Redfern method gave meaningless results although the genetic algorithm method gave acceptable results. As a result, it can be said that the Coats-Redfern method would not be used for reactions having low activation energies.