In this study, the preparation of polyaniline/polyvinyl alcohol (PANI/PVA) emulsion and the fabrication of PANI/PVA nanocomposite and electrochromic device are presented systematically. The surface morphologies, chemical structural and mechanical properties of the PANI/PVA nanofibers were characterized using scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and instrumental equipment. Four PANI/PVA composites with different PANI concentrations (i.e. 0 wt%, 0.2 wt%, 0.4 wt%, 0.6 wt%) were prepared to investigate the effects of PANI content on the electrochemical properties of the composites. Electrochromic properties of these PANI/PVA electrospun composite nanofibers are systematically characterized by an electrochemical workstation. Cyclic voltammetry was conducted to measure the electrochemical behavior of the PANI/PVA electrospun composite nanofibers at scanning speeds of 5 mV/s, 20 mV/s, 50 mV/s and 100 mV/s; it could be found that the redox peaks almost disappear. The discoloration of PANI/PVA composite electrospun nanofiber presents the color changing among the three mainstream colors of green, yellow, and blue.