This work is devoted to the modeling and simulation of hybrid electric vehicles with two sources of energy: a combustion engine and an electric motor. The Series / Parallel architecture is adopted for modeling, and each part of the traction is modeled separately. The constructed vehicle's model for simulation consists of assembling different blocks by connecting components in a structured manner with respect of the physical causality. For the control of the powertrain, a strategy is developed, whose role is to choose at every moment the best power distribution between the different energy sources in order to minimize fuel consumption and pollutants emissions.