The invention relates to a helix slow wave structure, which belongs to the field of microwave vacuum electronic techniques. The helix slow wave structure comprises a helix, a tube shell and n (n is larger than or equal to 2) dielectric clamping rods. The inner diameter of the helix is a, the outer diameter of the helix is b, the pitch of the helix is p and the helix is formed by a belt-shaped metal wire with a rectangular cross section in a winding way, wherein the length s of the rectangular cross section is equal to b minus a, the width of the rectangular cross section is w and s/w is larger than or equal to 1; n grooves which are in parallel with the central axis of the helix and are evenly distributed on the external surface of the helix; and the shape of the side surface of the dielectric clamping rods in contact with the tube shell is adaptive to the shape of the internal surface of the tube shell, the shape of the side surface of the dielectric clamping rods in contact with the helix is adaptive to the shape of the grooves arranged on the external surface of the helix and therefore the dielectric clamping rods can fix the helix in the tube shell to keep the central axes of the helix and the tube shell to be consistent with each other. By adopting the thicker helix, the helix slow wave structure provided by the invention has the advantages that the electron bombardment resisting capacity of the slow-wave structure is improved, the structure is firmer and the reliability is improved; and moreover, since the contact area between the dielectric clamping rods and the external surface of the helix is larger, the heat dissipating capacity of the slow-wave structure is further improved.