Abstract: Oxide cathode has been the most widely used in vacuum devices as an electrons emission source. In order to adapt the durative development of microwave devices to high power, wide frequency and long lifetime, a great deal of efforts has been devoted to search for the large emission current and high reliability oxide cathode. In this paper, we discussed the emission process of oxide cathode, the problem of conventional oxide cathode and the resolve method. So a new type of oxide cathode is developed and its DC and PC emission properties, lifetime and applications in TWTs and klystrons are studied, which indicates that oxide cathode have research potential and good applications prospects.