The characteristics of interference effect components of DC power transmission lines on telecommunication lines are discussed. Based on the current working mode and electrical features of power transmission lines and telecommunication lines, the equivalent disturbing current method is recommended for the project evaluation of noise meter’s electromotive force, by simplifying or neglecting some components. The calculation formula of interference effect doesn’t need to consider the attenuation coefficient. The research results could provide a basis for the compiling of the power industrial standard DL/T 5340 “Technical code for designing of telecommunication lines against danger effects from DC power transmission lines.”