Abstract: The tundish nozzle clogging samples were taken and analyzed. The clogging causes are understood. Main cause is Al₂O₃ inclusion and hercynite inclusions stick on the nozzle wall and accumulated. By feeding Φ13.5mm CaSi cored wire, the rate of feeding was 120~130m/min or 0.26~0.86 kg/t. The high melting point inclusions were changed into low melting point complex oxides. There was no longer tundish nozzle clogging observed. The most part inclusions were modified into spherical inclusions and their size was small.