Abstract: The working principle of the clinotron is slightly tilting the electron beam to the surface of the slow-wave system, optimizing the length of the effective interaction by varying the angle of the electron beam to obtain high output power and efficiency. The clinotron can be used as a new type of high power THz device. The development of the clinotron in foreign countries was reviewed in this paper. Moreover, we preliminary designed the physical dimension and the electrical size of the W-band clinotron ,and also investigated its “cold” characteristic.