Abstract: In order to investigate the effect of surface properties of nanometer materials on their performance of selectively reducing major harmful components in cigarette smoke,hydrophilic nanometer SiO₂ was modified by trimethylsilyl chloride silane,and the SiO₂ samples before and after modification were separately added into tobacco or filter tips for studying their functions. The results showed that: the hydroxy group was basically disappeared from the surface of modified nanometer SiO₂ and the sample exhibited hydrophobic property. When the modified nanometer SiO₂ was added into cut tobacco, about 27% of phenol and 12% of crotonaldehyde were removed from mainstream cigarette smoke, and CO content decreased slightly. Contrarily,the contents of phenol,crotonaldehyde and CO in the samples containing hydrophilic nanometer SiO₂ increased to different extents. Similarly,when the modified nanometer SiO₂ was added into filter tip, about 13% of phenol and 8% of crotonaldehyde were removed from mainstream cigarette smoke,while hydrophilic nanometer SiO₂ was inoperative. Therefore,the hydrophobic property of nanometer materials plays an important role in selective adsorption of weak-polar harmful components in cigarette smoke.