The invention provides a determination method and device of the nominal voltage of a lightning arrester along a half-wavelength power transmission circuit. The method comprises steps of firstly, determining basic information of the lightning arrester along the half-wavelength power transmission circuit; then, determining the nominal voltage and the maximum absorption energy tolerance level of thelightning arrester along the half-wavelength power transmission circuit; and finally, judging whether the configuration requirements of the lightning arrester along the half-wavelength power transmission circuit are met so as to obtain the final nominal voltage of the lightning arrester along the half-wavelength power transmission circuit. According to the invention, the overvoltage protection level, the operation impact residual voltage, the temporary overvoltage tolerance performance and the maximum absorption energy tolerance level of the lightning arrester along the half-wavelength power transmission circuit are determined; basis is provided for the model selection of the lightning arrester along the half-wavelength power transmission circuit; and a problem of the failure to coordinateand control the power fluctuation overvoltage of the half-wavelength power transmission circuit, the restraining of the operation overvoltage and the tolerance ability of the lightning arrestor is solved.