In order to detect the humidity and the density of cigarette, we designed a type of microwave resonance cavity sensor which is called repeating-entry model. We used TM010 resonance model to the real-time detection of cigarette humidity and density. Under two conditions: vacuum resonance and cigarette in existence, through the swept technique we obtain resonance frequency，peak powerand half power point bandwidth from amplitude-frequency peculiarity (Figure I). According to mathematical formulas (6) and (7), we get cigarette humidity and density respectively. The detection technique has many advantages such as speediness, continuation, high resolution rate, non-pollution, safe and convenient operation, etc. And it is applicable to industrial survey on the spot.