The invention relates to a high-order harmonic propagation coefficient test analysis method and device for a power transmission and distribution line. By virtue of analysis of nonlinear load harmoniccurrent transmission and transmitting characteristics, it is found that along with high frequency of the nonlinear load harmonic frequency, cable formation of the distribution line and improvement ofthe nonlinear electrical load grid-connected voltage grades, the problem that the high-order harmonic current resonance amplification caused by the power transmission and distribution line is gradually worsen; and by correctly calculating the characteristics of the power transmission and distribution line on the high-order harmonic transmission, important practical meaning is achieved to handlingof the high-order harmonic problem of the power grid and improvement of the operation safety of the power grid, thereby making up the blank of testing and analyzing the high-order harmonic propagationcoefficient of the power transmission and distribution line in the prior art.