Abstract: A combined emulsification technique was introduced to intensify emulsification by means of ultrasonic and mechanical stirring. Effects of ultrasonic power，ultrasonic frequency，emulsification temperature and time on the dispersity of water in heavy-oil by the combined technique or ultrasonic stirring alone were investigated on the basis of Sauter mean diameter（SMD）calculation. Results showed that the combined technique could achieve a higher dispersity of water with a 4—8 μm decrease in SMD of the disperse phase. The dispersity of water increases with the increase in ultrasonic power and emulsification temperature，while the emulsification temperature should not be higher than 90 ℃. Lower ultrasonic frequencies are favorable to the micronization of water in heavy oil. With the increase in emulsification time，the dispersity of water first increase and then decrease. As a result，the optimal experimental conditions can be considered as is 500—600 W of ultrasonic power，25—40 kHz of ultrasonic frequency，70—80 ℃ of emulsification temperature，and about 30min of emulsification time.