The invention discloses a reduced scale equivalent physical experiment method for an electric transmission line, and belongs to the technical field of high voltage overhead power transmission. The method comprises the steps that firstly, an electric transmission line reduced scale equivalent physical experiment is set in an ultra-long distance and large-capacity half-wavelength (3,000 km) power transmission mode; secondly, three reduced scale schemes of an equal proportion reduced scale, an equal electric conductivity reduced scale and an equal radius reduced scale are provided according to the relation among the reduced scale multiple, frequency and half wavelength of the electric transmission line reduced scale equivalent physical experiment; the equal electric conductivity reduced scale scheme is selected preferentially through calculation and comparison. Compared with an existing method for researching electric transmission line transmission characteristics, the equivalence before and after the electric transmission line reduced scale can be ensured, and a real electric transmission line is accurately simulated. The method has the advantages that a circuit is easy to construct and the equivalence is good, and has the good application prospect on the occasion that the electric transmission line needs to be used for performing an experiment.