The nano--crystal composite WO_3-TiO_2 photocatalyst was prepared by ultrasonic as-sisted sol--gel process. The effects of various factors, such as the crystal form, thesubstrates, the pH, the dissolved oxygen and the ultrasonic on the photocatalytic ac-tivity were investigated in view of the photodegradation of Rhodamine B. The resultsshow that the crystal form of WO_3-TiO_2 film with highest photocatalytic activity isrutile. The introduction of ultrasonic to the course of preparation can accelerate thedeposit time of the sol and increase the photocatalytic activity significantly in view ofthe highest photodegradation of Rhodamine B being 72.7% in 5 hours. The poroustitanium plate is the most suitable substrate in four kinds of investigated materials.Meanwhile the smaller the pH and the higher the concentration of the dissolved oxygenin the solution is, the higher the photodegradation is. The nano-crystal composite WO_3-TiO_2 photocatalyst was prepared by ultrasonic as-sisted sol - gel process. The effects of various factors, such as the crystal form, the substrates, the pH, the dissolved oxygen and the ultrasonic on the photocatalytic ac -tivity were investigated in view of the photodegradation of Rhodamine B. The resultsshow that the crystal form of WO_3-TiO_2 film with highest photocatalytic activity isrutile. The introduction of ultrasonic to the course of preparation can accelerate the deposition time of the sol and increase the photocatalytic activity was significantly in view of the highest photodegradation of Rhodamine B being 72.7% in 5 hours. The poroustitanium plate is the most suitable substrate in four kinds of investigated materials. However, the smaller the pH and the higher the concentration of the dissolved oxygen in the solution is, the higher the photodegradation is.