Abstract: In order to investigate the factors influencing the fluctuation of draw resistance of slim cigarettes during smoking, a puff-by-puff draw resistance measuring system was developed, and the effects of tipping paper permeability and cut tobacco structure on the fluctuation of puff-by-puff draw resistance of slim cigarettes under ISO smoking regime were studied. The results showed that:1) Perforated tipping paper reduced the fluctuation of puff-by-puff draw resistance during smoking; the higher the tipping paper permeability was, and the smaller the fluctuation of puff-by-puff draw resistance would be. 2) The fluctuation of puff-by-puff draw resistance was smaller when the short strand proportion was higher; the fluctuation range significantly correlated to the proportion of long strands with length/width ratio > 6 and width > average width, and those larger and longer strands reduced the size uniformity and filling power of cut tobacco.