Abstract: To selectively reduce HCN in cigarette smoke, transition metal ion functionalized poly(ethylenimine) (PEI) material was prepared and characterized by UV-vis and thermogravimetric (TG) analysis. An experimental setup to simulate cigarette filter was used to evaluate the capability of the material to reduce HCN. The material preparation conditions were optimized and the final materials were applied to cigarette by paper coating method onto the paper filter segment of the paper-acetate dual filter. The results showed that:1) The modified PEI featured high water solubility and thermally stable below 280℃. 2)The optimal preparation condition of the material was:PEI MW 600, PEI concentration 20%(W/W), and the ratio of Zn²⁺ to PEI 2.93×10^-4 mol/g. 3) Comparing with the control, the HCN in mainstream smoke from cigarettes with filters containing 10.6 mg PEI per cigarette was selectively reduced by 40.2% while tar level and sensory quality of the cigarettes were basically unchanged. At an addition rate of 19.9 mg per cigarette, the selective reduction rate of HCN reached 72.1%, but the sensory quality of the cigarette deteriorated.