A zigzag slow-wave line of double ridged waveguide belongs to the technical field of microwave vacuum electron and relates to a traveling-wave tube amplifier. A slow-wave structure is formed by periodically bending the double ridged waveguide (4) along the electric field to form a right-angled zigzag line or a U-shaped zigzag line; circular through holes are arranged at the positions along the mean axis symmetric line (2) of the slow-wave structure on the waveguide wall; and the slow-wave lines are connected by the metal tubes (3) with the aperture the same with that of the circular through holes between two circular through holes of the right-angled groove or U-shaped groove in each zigzag periodic structure of the slow-wave structure to form an electron stream channel. Compared with conventional zigzag slow-wave line of waveguide, the slow-wave line has lower cut-off frequency, wider pass band range and flatter dispersion characteristics. In addition, in the event that the dispersioncharacteristics are approximate, the zigzag slow-wave line of double ridged waveguide has smaller cross-sectional dimension to well ensure the transfer characteristics of electron stream in travelingwave tube under the action of the same focusing magnetic field, so as to improve the integral output power and grain of the traveling wave tube.