Abstract: Ultrasonic treatment was used by way of an ultrasonic wave probe directly inserted into molten steel to improve the cleanliness of steel and decrease the amount of inclusions in steel. A comparative study of ultrasonic and argon-blowing treatment was carried out on inclusion removal efficiency in molten steel. Experimental results showed that the amount of inclusions decreased when the ultrasonic wave was inputted into molten steel. But the inclusions removal rate was low, about 4% to 12%. When ultrasonic treatment was carried out solely, with decreasing power and increasing treatment time, the inclusions removal rate was increased. When argon-blowing was carried out solely, the inclusions removal rate was high, from 29% to 41%. With increasing argon-blowing flux, the inclusions removal efficiency was found a trend of rising.