Abstract: For detecting the toxic vapors in atmosphere, the homogeneous solution was prepared with nature cotton fiber and chitosan in 1-butyl-3-methylimidazolium chloride (BMImCl) ionic liquid. The multiwall carbon nanotubes (MWCNTs) with sodium dodecyl sulfate (SDS) modification were used as the conductve fillers. And MWCNTs/cellulose-chitosan conducting composites used for gas sensor were successfully prepared by using solution coating method. Results show that when the mass ratio of chitosan to cellulose is 1:7, MWCNTs/cellulose-chitosan composites show better gas-sensing properties, reproducibility and stability for polar organic solvent vapors methanol, ethanol, chloroform and acetone at percolation value of about 2.8wt%. The gas-sensing response behavior of MWCNTs/cellulose-chitosan composites shows typical negative vapor coefficient (NVC) effect.