The objective of this paper is to present the system construction and operational principle for a DC charger of electric vehicle. By means of analyzing AC and DC sides for the chargers, a reason was derived theoredically for producing specified harmonic current while absorbing fundamental wave of electric power system. The modeling and measuring procedures of multi-harmonic source for single and multiple chargers were proposed. The summation effect of harmonics for charge/exchange station which was regard as a public coupling circuit(PCC) of the electric power system. The simulation and measuring results indicate that as a new type of nonlinear load, the charger represented a characteristic of steady-state harmonic source.