Abstract: WO₃ has been widely used because of its excellentperformance in Electrochromism.The article introduces preparationof WO₃ film,illustrates that the Faughnan’ s model is the most widely accepted electrochromicmechanism of WO₃ film, summaries that the optical amplitude modulation and amorphizationhave great significance forelectrochromic performance of WO₃ film according to the literature of recent years. Though WO₃ films have some practical application in our life,the advantages of long response time and poor stability restrict the range of application. Finally,The composite material film composed of polymer and WO₃ represents the main developing trend of WO₃ film are known.