Abstract: Helix traveling wave tube is widely used in wideband and high gain traveling wave power amplifier devices. The attenuator is one of the key components to improve the stability of the tube performance. It can not only absorb the reflected wave caused by the change of transmission medium at the input, output and termination of the tube, but also suppress the self-oscillation caused by the superposition of the reflected wave and the forward wave; moreover, it can reduce the influence of impedance mismatch generated by the transmission circuit at the input, output and cut-off end, and expand the effective propagation frequency band width of the traveling wave tube. At the same time, discharge or arcing caused by charge accumulation on the ceramic rod can be avoided. This paper mainly expounds on the process requirements from material selection to the preparation process of carbon film attenuators. By adjusting the temperature, heating time, chamber air pressure, and gas flow factors, the carbon film attenuator that meets the design requirements of the helix traveling wave tube is prepared.