Abstract: In order to real-timely detect and reject the defective cigarettes caused by tipping paper with uneven gluing or misalignment, an online detecting and rejecting system was designed basing on the variations of electromagnetic energy parameter of microwave versus glue amount. The microwave signal generated by a microwave media resonator was time-sharingly sent to a microwave resonant cavity by a single-pole multiple-throw microwave PIN switch. The variation of output signal from the resonant cavity would indicate that whether the tipping paper was properly glued. The application results showed that the system could online detect and reject the cigarettes with tipping paper gluing defects, the smallest detectable area of glue missing was 2 mm×2 mm, and the effective rejecting rate was up to 96%. The quality of tipping paper gluing was well controlled and appearance quality of cigarette was improved.