Abstract: Tungsten trioxide thin films were deposited on quartz-glass substrates by the RF sputteringtechnique, and the current-voltage characteristic and microstructure of WO₃ thin films were investigated. The WO₃ thin film is polycrystalline film with grain size below 100nm, and it exhibits a good varistorbehavior with the nonlinear coefficient α＞10 calculated in the current ranges of 0.1mA to 1mA. Somequestions related to nonlinear electrical transport mechanism were discussed briefly.