Abstract: In order to investigate the effects of filter ventilation on the releases of routine components and seven harmful components in mainstream smoke of slim cigarettes, slim cigarette samples with different filter ventilation rates and cigarette paper of different air permeabilities were prepared. The releases of routine smoke components and seven harmful components in mainstream smoke were analyzed under machine-smoking conditions. The results showed that:1) The total ventilation rate, filter ventilation rate, paper ventilation rate negatively correlated to the releases of routine smoke components, the seven harmful components and the cigarette harmful index (H). 2) When the total ventilation rate, filter ventilation rate or paper ventilation rate increased by 1%, the reduction rates of CO, HCN and crotonaldehyde were higher. The influences of paper ventilation on the releases of TPM, tar, nicotine, CO, moisture, HCN, NNK, phenol and crotonaldehyde and the H index of slim cigarettes were greater than those of filter ventilation alone. 3) The influences of filter ventilation and paper ventilation on the releases of tar, nicotine, CO, HCN, ammonia and phenol and the H index of slim cigarettes were slighter than those of king-sized cigarettes. By optimizing the ventilation parameters, the releases of tar and seven harmful components in mainstream smoke of slim cigarettes could be reduced.