The invention discloses a wideband traveling wave tube slow wave system and a fabrication method thereof. The wideband traveling wave tube slow wave system comprises a tube (3), clamping rods (1) and a spiral line (2), wherein the clamping rods (1) are symmetrically arranged inside the tube (3), the outer sides of the clamping rods (1) are connected with the inner surface of the tube (3), and the spiral line (2) is arranged on the inner sides of clamping rods (1) and connected with the adjacent clamping rods (1). The fabrication method comprises the following steps as fabricating the tube (3), fabricating the clamping rods (1), fabricating the spiral line (2), assembling, and testing. Through the invention, the working band range of the slow wave system is increased by 50-150%, and working band is up to 2.4 octaves. The traveling wave tube fabricated with the wideband traveling wave tube slow wave system is especially suitable for electronic countermeasure. The invention will greatly widen the application range of the traveling wave tube.