For some applications such as variable branch protection and user-side protection in distribution network that need to calculate the steady-state current and voltage values as soon as possible, how to deal with current and voltage transient fault signal in a short period of time has become a problem that we face. The existing power grid fault signal processing methods are usually limited in the length of sampling data and the quantity of parameters with the result that the count of current and voltage fault transient signal is hard and takes a long time. This article was based on the characteristics of fault transient voltage and current in distribution network, and established a model including stable-state power frequency component and decaying DC component to approximately characterize distribution network fault transient voltage and current. The particle swarm-Gauss Newton hybrid algorithm was used to identify the parameters of this model and the transient parameters were obtained. The simulation analysis and engineering application have proved that it has a better approximate effect and robustness than former algorithms.