Because of the existence of primary user signals and the inevitable nonlinearity of some RF devices

the inter-ference signals such as three-order intermodulation signal would be produced in the front-end of RF receiver.To reduce the impact of interference signals

the interference which was caused by primary user signals to dynamic spectrum shar-ing wireless communication system was analyzed on the front-end of RF receiver side.Then

the restriction on opera-tional channel selection of dynamic spectrum sharing wireless communication system was derived.By following the re-striction

the negative effects caused by interference signals could be reduced and the quality of communication in dy-namic spectrum sharing system was guaranteed.Finally

availability of the restriction on operational channel selection is verified experimentally in UHF dynamic spectrum sharing wireless communication system.