The short millimeter wave and Terahertz Traveling Wave Tubes(TWTs) possess the advantages of wide bandwidth, high power and high efficiency, which show application prospects in military and civil fields such as high-resolution imaging, high-speed communication and electronic countermeasures. The development level of domestic and foreign companies and TWTs developed by author in recent years are analyzed and reviewed, covering several frequency bands such as E-band, W-band, G-band and Y-band. In order to further enhance the output power of TWTs, the technical analysis and experimental research are carried out on the innovative Folding Waveguides(FWG) structure, Phase Velocity Tapering(PVT) technology, band injection Periodic Cusped Magnet(PCM) clustering, multi-injection integration, etc., laying the technical foundation for device performance enhancement and application promotion.