The research and development activities of near-terahertz linear beam vacuum electronic devices are described, including slow wave structure theory, parts design, simulation and optimization, micro-fabrication and micro-assembly techniques, tube integration technologies, etc. These devices include Traveling Wave Tubes(TWTs), Backward-Wave Oscillators(BWOs), clinotrons, Stop-Band Oscillators and TWT harmonic amplifiers, etc with folded waveguide and vane-loaded waveguide as high frequency interaction structures. The devices technologies are mainly composed of Micro Electro Mechanical System(MEMS) technology, Microwave Plasma Chemical Vapor Deposotion(MPCVD) diamond process, metallization and mounting technique, etc. Finally, specifications of devices at W-band, 220 GHz and 340 GHz frequency bands are given.