Polyoxometalates (POMs) are a kind of metal oxide nanoclusters with excellent electrical properties, which have proved to be an excellent candidate for electrochromism (EC) materials. In this paper, we present a better performance POMs-based EC material on the TiO2 substrate through adjusting the structure of the Well-Dawson type POMs with the electrodeposition method, which can overcome the high cost of the traditional methods such as vacuum evaporation or sputtering. The performance of the EC smart windows was fully tested. The maximum optical contrast for the K10[P2W17O61]·20H2O (P2W17)-based EC smart window is 93.1% at the wavelength of 620nm and for the K6[P2W18O62]·14H2O (P2W18)-based EC smart window is 48.7% at 646nm. The coloration time extracted for a 90% transmittance for the P2W17-based EC smart window is 0.9s and for the P2W18-based smart window is 0.97s; the coloration efficiency for the P2W17-based EC smart window is 205.3cm2 C−1 and the P2W18-based smart window is 176.8cm2 C−1. Both of the P2W17- and P2W18-based EC smart windows have the feature of remarkable durability over 1000 cycles. The P2W17-based smart window has larger optical contrast and higher coloration efficiency than the P2W18-based smart window. More significantly, the near-infrared behavior of the P2W17 under different applied potentials was recorded for the first time by using the smart window. We believe the performance of the P2W17-based smart window is the state-of-the-art among the POMs-based EC smart windows.