Parametric identification method of power electronic circuits is studied in this paper. The electrolytic capacitors feature parameters can be obtained by setting the monitoring signals based on this method. The new method based on finite difference method and genetic algorithm for the parameter identification of power electronic circuits is proposed. Taking the BuckBoost converter circuit as an example, the parameter identification of power electronic circuits is achieved. Firstly, the BuckBoost converter’s transfer function model is established. Secondly, the output voltage and the inductor input voltage are selected as monitoring signals. The finite difference method is used to preliminary calculate and the genetic algorithm is used to estimate the circuit’s parameter. The experimental results show that the new method can be effectively applied in the parameter identification of power electronic circuits.