The invention relates to a manufacturing process of a slow wave system for a helix travelling wave tube. The manufacturing process comprises steps that, (1), a helix and a clamping rod are put in a tube casing to form a slow wave before extrusion; (2), the slow wave before extrusion is put in an extrusion tool, the position corresponding to the clamping rod is aligned with a pressing head of the extrusion tool, pressing force is exerted through the extrusion tool to make the tube casing, the clamping rod and the helix to realize tight contact; (3), a white copper ring and a pure iron pole shoe are sleeved outside the tube casing, an AgCu welding material is filled, and the parts are sent to a hydrogen furnace; (4), the temperature curve of a hydrogen furnace is set as follows, the temperature increasing/decreasing speed is 15DEG C/min, the soldering temperature is 780 DEG C, the insulation time is 2 minutes, and the parts are taken out after soldering; and (5), whether the clamping rod and the helix of the slow wave system generate displacement and whether the welding material is fully melted are detected through a microscope. According to the manufacturing process, structure soundness and thermal diffusivity of the slow wave system are greatly improved through the hot compression effect, and bearable power of the whole tube can be improved correspondingly.