Abstract: In order to investigate the effects of cigarette circumference on combustibility and smoke aerosol properties, the solid phase temperature of cigarette combustion cone and gas phase temperature in filter tip of the same brand cigarettes with three circumferences (Ø24.37 mm, normal; Ø20.06 mm, medium; Ø17.02 mm, slim) were tested by infrared thermal temperature and thermocouple temperature measurement technologies, respectively. A smoking cycle simulator and a fast particle spectrometer were employed to determine the particle size of mainstream smoke aerosol under ISO smoking regime. The results showed that: 1) The solid phase temperatures of the medium and slim cigarettes were higher than those of the normal cigarette by ~100℃ on average under puffing. 2) The gas phase temperatures at the filter front of the medium and slim cigarettes were higher than that of normal cigarette by ~5℃. However, the gas phase temperatures in the filters of the three sizes of cigarettes tended to be consistent. 3) With the decrease of cigarette circumference, the average particle number concentration of aerosols for all puffs increased significantly, while the count median diameter (CMD) decreased, which indicated that the number of fine particles increased. 4) With the decrease of circumference, the average particle surface area of aerosols for all puffs increased significantly, and the area median diameter (AMD) reduced, which suggested that the total area of fine particles increased significantly.