Abstract: In order to investigate the relationship between cut tobacco structure and the burning cone drop of slim cigarette, the samples of three slim cigarette brands were tested, the burning cigarette was in-situ fixed with embedding method to obtain the slices of the tobacco rod and its burning cone. The cut filler in the slices was analyzed through optical microscopy. The results showed that:1) The axial distribution of cut tobacco density varied widely, therefore the tobacco rod was divided into four sections:section a(0-6 mm from the lit end of cigarette), section b(6-20 mm from the lit end), section c(20-50 mm from the lit end)and section d (50-65 mm from the lit end). The rate of burning cone drop increased with the rise of △ ρ, the difference between the maximum density in section b and the minimum density in section c. 2)The higher the proportion of medium and short shreds in cut filler was, the shorter the burning cone would be, and the higher of the structure evenness in the burning cone would be. 3)The drop rate of the burning cone of brand B decreased from 58% to 28% when the flat ecreteur disc was replaced by a U-shaped ecreteur disc. 4)When the proportion of medium and short shreds in cut filler increased from 10% to 35%, the drop rate of the burning cone of brand B reduced from 42% to 20%.