Abstract: In order to selectively reduce the levels of hydrogen cyanide(HCN)and crotonaldehyde(CRA)in mainstream cigarette smoke, 20 natural amino acids were screened with a simulated filtration device to test their toxicant reduction performance as filter additives. Lysine was selected for the synthesis of fumed silica adsorbed lysine ionic liquid(Ch Lys/SiO₂)adsorbent material(60-80 mesh fine particles). The structure of Ch Lys/SiO₂ adsorbent material was characterized, and its toxicant reduction performance was measured. In addition the material was applied to a dual-segment filtered cigarette, and the sensory quality of cigarette smoke was evaluated. The results of toxicant reduction performance test showed that lysine in the filter was effective in the reduction of HCN and CRA(P<0.01); Ch Lys/SiO₂ was more effective than lysine, it reduced the release of HCN and CRA in mainstream cigarette smoke by 83% and 29%, respectively; the reduction rates positively linearly correlated to the dosage of Ch Lys/SiO₂ within the range of 0-0.3 mmol/cig. Cigarette application results indicated that when ChLys/SiO₂ was added to a dual-segment filter at a rate of 0.08 mmol/cig, the release of HCN and CRA was reduced by 28% and 10% comparing with the control, respectively. The variations of release of tar, nicotine and other typical harmful components, such as CO, NH₃, NNK, benzoapyrene and phenol were negligible. The sensory style of cigarette did not change significantly(P>0.05).