Vacuum electronic devices, with the natural advantage of high power in millimeter wave and terahertz bands, can be applied to construct high-efficiency and high-power radiation sources. This is of great significance to the development of high-power microwave technology and terahertz technology. The output window is one of the key components of vacuum electronic devices. The breakdown of the output window mainly accounts for the failure of the devices. The multipactor is considered as the main reason for the breakdown of the output window. This paper summarizes current advances of output window in the decimeter and centimeter-wave bands. On this basis, the tendencies of this research fields are predicted in order to provide reference for the future development of vacuum electronic devices in higher power and higher frequency levels.