A polyaniline (PANI)/silica (SiO2) composite film was prepared by a simple in situ electrodeposition method, and its electrochromic (EC) properties were studied. When PANI was electrodeposited in the presence of SiO2 particles, the resulting PANI/SiO2 composite films possessed higher surface areas, larger redox charge capacities, and higher doping levels, thus enhanced optical contrasts. By incorporating SiO2 particles into the PANI film, the transmittance change at 700nm from 10.7% to 16.4%, or an enhancement of ca. 50%, was achieved when operating between −0.5V and 0V. In addition, x-ray photoelectron spectroscopy (XPS) indicated that the formation of the highly oxidized PANI might have been retarded through the addition of SiO2 particles. Furthermore, the growth mechanism of the PANI/SiO2 composite film was proposed.