This paper defines power ultrasonics and their two important directions: Ultrasonic emulsification and dispersion from a practical point of view, brief reports on recent research results are ultrasonic emulsification to be used for the preparation of composite electrorheological fluid, and ultrasonic dispersion to be used dispersion as a new type cold cloud catalytic agent metaldehyde [CH3CH]4-6 (this is used for artificial rain), etc., and produce good results or gain progress. Then, the principle and applications of power ultrasonics (including magnetostriction type ultrasonic transducer and piezoelectric type ultrasonic transducer) in the emulsification or dispersion, are pointed out. Also, ultrasonic extensive applications in chemistry, materials, and life sciences are briefly introduced.