Abstract: To study the influence and the mechanism of cut tobacco width on the CO release in mainstream cigarette smoke, the burning cone temperature of lit cigarettes made from tobacco of different cut widths was measured by a thermocouple method. The temperature distribution of the burning cone during machine-smoking was obtained via fitting of experimental results, and the correlation between the temperature distribution and CO release was analyzed. The results showed that:1) Cut tobacco width affected the shape and temperature distribution of the burning cone significantly. The total cone volumes and the high temperature (>600℃) section of the cone increased, while the low temperature (200-400℃) volume section of the burning cone decreased with the increase of cut width. 2) CO release mainly concentrated in two temperature ranges, 360-480℃ and 540-730℃ respectively, while the CO release below 350℃ was very low in comparison. 3) Mainstream CO release increased with the rise of characteristic temperature T_0.5 of the burning cone. T_0.5 could be effectively decreased by adjusting cut tobacco width so as to reduce CO release. When the proportion of tobacco at 1.5 mm cut width was 20%, T_0.5 decreased by 31℃, CO release was reduced by more than 1 mg/cigarette, and the hazard index of cigarette decreased accordingly.