The work aims to study electrochromic properties of tungsten oxide dihydrate films with different microstructures. Tungsten oxide dihydrate films were prepared on FTO by chemical solution deposition method. Different nanostructured WO3?2H2O films were synthesized by adding different morphology control agents (citric acid or ammonium oxalate). The com-position and microstructure of the films were analyzed by X-ray diffraction (XRD) and scanning electron microscopy (SEM). UV-visible spectrophotometer was used to study the transmittance of films with wave length within 200~1000 nm and electro-chromic performance of the films was investigated by an electrochemical workstation. The transmittance of WO3?2H2O film prepared with citric acid as the morphology control agent reached 82%, and the transmittance difference of film in colored and faded state was 36.2%. The WO3?2H2O films prepared by adding citric acid or ammonium oxalate as the morphology control agent exhibited nano-sheet structure. The thickness of the nanosheets was 5~15 nm and 50~60 nm, respectively. However, WO3?2H2O prepared with citric acid had more gaps and cracks, which exhibited better electrochromic properties. WO3?2H2O film with gaps and cracks increases the contact area between the film and the electrolyte, and reduces the path distance of ion diffusion. The smaller nanostructures can provide more chemically active sites, thus showing better electrochromic properties.