By incorporation of a special cigarette smoke generator and air circuit switching and dilution techniques, a device for real-time determination of the aerosol concentration in mainstream cigarette smoke puff by puff was set up, and the samples of 5 cigarette brands were tested. The results showed that the device worked stably, the average number of the aerosols of the 5 samples ranged from 1.39×109 to 3.71×109 per cm³ with the variation coefficient below 9%.