The electrospinning technique was utilized to produce camphorsulfonic acid (HCSA) doped poly (0-toluidine) (POT)-polystyrene (PS) composite fibers in the non-woven mat form with different fiber characteristics, depending on the proportion of components in spinning solutions. It was observed that as the concentration of PS increased, tiber diameters increased with a reduction of the quantity and size of beads on the fibers. However, when the POT content was increased, fiber diameters decreased with increasing amounts of beaded fibers. The beaded tibers could be attributed to POT accumulation during solidification from the tip of the pipette to the collector. The amount of HCSA also att'ected the surface morphology of HCSA doped POT-PS composite fibers. As the content of HCSA increased, fiber diameters slightly changed and smaller amounts and sizes of beaded fibers were obtained due to the high static charge of the spinning solution and great solubility of POT in the doped form. HCSA doped POT-PS composite fibers were fabricated on an interdigited gold (Au) substrate for use as a chemical vapor sensor. The composite fiber sensor responded to volatile chemicals in different ways, depending on the polarity ofsensing chemicals. The resistance of the composite fiber sensor was decreased in the case of high polar solvent sensing measurement whereas the resistance of the sensing electrode was increased when exposed to low polar solvent. The response value or the composite fiber sensor increased with an increasing sensing chemical polarity. The surface morphology of the non-woven composite fiber mat alter chemical vapor sensing was unchanged, implying that the electrospun composite tiber sensor could be reusetl Tor several times