Abstract: Vacuum nano-diodes and nano-triodes have basic functions similar to traditional vacuum tubes, but can be manufactured by the most advanced micro-fabricating line to achieve small size, light weight and high integration, which makes them a rapid development in the past decade. The origin, development process and state-of-the-art of vacuum nano-diodes and nano-triodes are reviewed. Typical nanoscale vacuum devices with lateral structure, vertical structure and gate-all-around structure are introduced, and their strengths and weaknesses are analyzed. Silicon devices are most compatible with the mature micro-fabrication process, but the devices based on metals or wide band-gap semiconductors, such as silicon carbide and gallium nitride, have better electrical properties, higher temperature resistance and stronger radiation endurance. Although the developing vacuum nano-diodes and nano-triodes still cannot compete with solid-state integrated circuits in most regular applications, they are attracting more attention and are expected to be employed in harsh conditions with high temperatures or strong radiations.