Abstract: In this paper, the effects of ultrasonic wave on viscosity reduction for Venezuela and Fengcheng ultra heavy oil are studied. Four types of ultra heavy oil examples are prepared for experiments: 80% Venezuela ultra heavy oil with 20% 0#diesel (Example I), 70% Venezuela ultra heavy oil with 30% 0#diesel (Example II), the oil-in-water (O/W) for Venezuela and Fengcheng ultra heavy oil (Examples III and IV) by using active macromolecule viscosity reducer. In the experiments, these four types of examples are irradiated by ultrasonic horn (18 kHz) and ultrasonic bath (24 kHz) respectively. Here are the results: (1) the viscosity of Example I irradiated by ultrasonic wave is 25% higher than that un-irradiated at 20 ℃, for Example II, 15% higher. (2) the obvious effects of ultrasonic wave on reducing viscosity can be observed for Example III whose viscosity irradiated by ultrasonic wave is 25% lower than that un-irradiated at 20 ℃ and 20% less quantity of active macromolecule viscosity reducer is needed. (3) For Example IV, no obvious effects are observed except at 14 ℃, where less than 25% viscosity reduction is observed for that irradiated by ultrasonic wave. The reason of the phenomenon observed in this paper is analyzed qualitatively.