<正> In the 30MHZ-1000MHZ frequency band, the oscillator or filter is constructed by high Q screw resonatores. However, we can convennient ly expand or compress the frequency band. In fact, it is impossible to make UHF, VHF oscillators or a filter with the crystal resonatores or composite paramenter devices, in the frequency board within the VHF higher end and UHF band. So it is most important to study the screw resonator for the design of the duplexing technology on the satellite, frequency multiplier, oscillator or polycavity screw filter.This article deals with the monocavity field distrubution, chromatic dispersion charactor and polycavity mutual inductance help each other and has made apractic film of the experiment.