Abstract: In order to study the radial diffusion and axial flow processes of cigarette smoke, SIMPLEC algorithm, second-order upwind algorithm and component transport method in computational fluid dynamics (CFD) combined with particle image velocimetry (PIV) were used. By taking CO as a representative component, the radial diffusion through cigarette paper and the axial flow of cigarette smoke were analyzed. The results showed that:1) The shortening of cigarette increased the percentage of CO in cigarette smoke diffused through the cigarette paper. 2) Within the porosity range of 0.415-0.482, the increase of cigarette paper porosity did not obviously affected the percentage of CO in cigarette smoke diffused through the cigarette paper, but it would increase CO level in cigarette smoke at the mouth end. 3) The increase of either the mean pore diameter of cigarette paper or the pressure at the mouth end increased the percentage of CO in cigarette smoke diffused through the cigarette paper and that come out of the mouth end.