Abstract: The effect of ultrasonic power on inclusions of high carbon steel with rare earth was investigated.The results show that ultrasonic treatment in molten high carbon steel with rare earth could can disperse,refine and remove the inclusions.With the increase of ultrasonic power,the total oxygen content of high carbon steel and the average diameter of inclusions decreases evidently,the inclusions of high carbon steel will be removed in a certain degree,but the number of inclusions increases significantly.The massfraction of total oxygen content in high carbon steel, the equivalent number I and the average diameter d of inclusions in ingots are 59 × 10^-6, 134 mm^-2, and 2.91 μm respectively when the ultrasonic power is 100W. At the same time, the number of inclusions less than 2.31 μm is more than 43% of the total.