WOx-Mo thin films have been deposited on the ITO/PET substrates by RF magnetron sputtering. The electrochromic properties of films were investigated by cyclic voltammetry (C-V) and chronoamperometry (CA) methods. It is found that the maximum of oxidation current increases and the oxidation peaks move to plus potential with increasing Mo doping concentration. Furthermore, the coloring response time decreases and the bleaching response time increases with increasing Mo doping concentration in the experimental range. For the film doped 15.4% Mo, the oxidation current reaches the maximum and the coloring response time is 4.53 s, the bleaching response time is 9.8 s. Not all the samples exhibit good reversibility due to the charge left in the film. The best reversibility is 51.2 % in the WOx film doped 7.6% Mo