Abstract: Ultrasonic cohesion and cavitation are discussed.The ultrasonic treatment experiment of particles in paraffin was carried out and the distribution situation of particles in paraffin after ultrasonic treatment was observed and analyzed with focus on the relationship of the particles cohesion in paraffin and ultrasonic processing time as well as ultrasonic power.The particles cohesion trend under different ultrasonic power for different processing time was observed,the photo of the paraffin samples was taken with digital camera,and the metallographic microscopy analysis was carried out,and then the size of the particle was estimated.At last,the optimum ultrasonic power while the particles-cohesion has the best effect in paraffin was determined.