Abstract: The natural vibration characteristics of cesium beam tube were analyzed,the dangerous frequency and the weakness of structure of cesium beam were obtained.The corresponding countermeasures were proposed,which are useful to the research of the cesium tube for space application.An experiment using the sine sweep method to identify the natural frequencies of cesium beam tube was conducted.Compared with the natural frequencies in experiment,it has been proved that the finite element model is reasonable and the calculation result is accurate.