A new calculation method for harmonic impedance of system side based on fault component is proposed． Based on the equivalent analysis model of harmonic pollution，the characteristics of harmonic voltage and current fluctuation at point of common coupling ( PCC) caused by the failure of the customer side are analyzed，and the harmonic impedance of the system side is accurately calculated by calculating the volt － ampere characteristic ratio of PCC． The simulation analysis and field data calculation results show that the proposed method can effectively avoid the interference of harmonic voltage fluctuation caused by point of common coupling on the system side，so as to obtain more accurate harmonic impedance value on the system side． The research work can be used to evaluate the level of harmonic emission and to divide the responsibility of harmonic pollution．