Abstract: In order to meet the rapid needs of millimeter-wave spectrum, such as satellite communication and wireless communication, the physical characteristics and design techniques of helix Q-band traveling wave tubes such as high power, high efficiency, high gain and nonlinearity are studied in detail. Through the theoretical analysis of the wavelength-size-matching effect, the dispersion characteristics and coupling impedance of the slow wave structure are studied, a double tape technique is adopted to improve the electronic efficiency while taking into account the high gain and good nonlinearity. The design method of main attenuation, input secondary attenuation and cut-off is adopted to effectively suppress the backward-wave oscillation to make the traveling wave tube work stably. And a five-stage collector is designed on the basis of the electronic spectrum analysis after interaction, and the efficiency of the collector reaches 90%, which promotes the improvement of the total efficiency of the traveling wave tube. Using the above design methods, two kinds of Q-band helix communication traveling-wave tubes were manufactured, and the test results are as follows: Type A high-power traveling-wave tube, Q-band (bandwidth 2 GHz), output power up to 125 W, total saturation efficiency up to 57%, saturation gain 45 dB, phase shift less than 49°, weight 460 g. Type B miniaturized traveling-wave tube, Q-band (bandwidth 4.5 GHz), saturated power 65 W, saturation total efficiency 55%, saturation gain 46 dB, phase shift less than 45°, weight 350 g. The two helix Q-band traveling wave tubes meet the requirements of high efficiency, high linearity, high gain, miniaturization and other comprehensive indicators of communication, and the test parameters exceed the latest public reported products, showing excellent comprehensive performance. The design method proposed in this paper provides an important reference for the research of Q band and higher frequency helix communication traveling-wave tubes.