This paper deals with the parameter determination procedure of a gas-discharge arrester's (GDA) model. As the accuracy of the model depends on its parameters, the goal of this procedure is to determine adequate parameter values so that the model's performances match the real device behavior as much as possible. In order to achieve this goal, differential evolution (DE), a stochastic optimization algorithm, is included in the determination process. The main task of the DE algorithm is to vary the model's parameters during the optimization process, thus minimizing the difference between the measured and model-calculated current and voltage time behavior. An accurate GDA model has been obtained on the basis of measurements on a single GDA test object. This model is relevant and suitable for a series of GDA devices as the agreement between their measured and model-calculated voltage and current time behavior is excellent.