Recrystallization during hot working has large influence on the final properties of the material. Therefore, many different approaches have already been developed in this direction to model this important phenomenon. In the diploma work we have used a new approach to model dynamic recrystallization based on mean field theory. A KM model was used to describe the evolution of dislocation density during deformation, grain growth was described by determining the energy of the system and using the Lagrangian formalism. To determine the onset of nucleation, we used the approach proposed by Roberts and Ahlblom. We investigated the influences of individual mechanisms on the kinetics of dynamic recrystallization, which were affected by the parameters of the model. The experimental flow curves and microstructures before and after hot plastic deformation for S690QL steel were used to determine the material parameters. We determined the model parameters to obtain the best agreement between the simulation and experimental results. It was found that the model responds well to variations in temperature and strain rate, and that it can describe all the phenomena and dependencies observed in the experimental results.