High sensitivity and selectivity of C-doped WO 3 gas sensors are reported in this paper. C-doped WO 3 is synthesized by a facile infiltration and calcination process using the cotton fibers as templates. The response of C-doped WO 3 sensor toward toluene (50 ppm) and xylene (50 ppm) reach 91 and 199, respectively. By comparing the response of C-doped WO 3 sensor toward various indoor noxious gases (toluene, formaldehyde, ethanol, methane, benzene, and xylene), distinctive selectivity toward toluene and xylene is found. In addition, C-doped WO 3 exhibits relative hygro-stability, differing from traditional gas sensor material. The results indicate that C-doped WO 3 has good potential in practical applications, due to its remarkable performance and facile synthesized methods.