Large-scale electric vehicles, as intermittent and impact loads, are connected to the distribution network, which will have a direct impact on the transient power quality of the distribution network with quick charging stations of electric vehicles. This paper mainly analyzes the transient power quality problems such as voltage sag and electromagnetic transient caused by large-scale electric vehicles connected to the distribution network. Firstly, the distribution network with EV quick charging stations is modeled. Secondly, the voltage sag model based on the transformer model and the electromagnetic transient analysis model based on the distributed parameter equivalent model are established. The transient power quality problem caused by the connection of quick charging station to distribution network is analyzed theoretically. The model can improve the speed and accuracy of transient simulation. The transient power quality problems in the normal switching and fault of the quick charging station are verified by simulation analysis.