Tungsten trioxide nanoparticles doped amorphous hydrogenated carbon (WO3/a-C:H) films were successfully fabricated on silicon substrates by electrochemical deposition technique under atmospheric pressure. The as-deposited films were characterized by X-ray photoelectron spectroscopy, Transmission electron microscopy, Fourier transform infrared spectroscopy and Raman spectroscopy, respectively. Results showed that nanocrystalline tungsten trioxide particles with a grain size in the range of 8–12 nm were homogeneously embedded in the amorphous carbon matrix, and the sp3-hybridized carbon content in the a-C:H films increased. Compared with pure amorphous carbon film, the hardness and elastic recovery were significantly improved due to the doping of WO3. At the end, an understandable model was proposed to interpret the growth mechanism of the WO3/a-C:H composite films.