Abstract: In this paper the fluorescence scanning results from the tundish nozzle clogging material in combination with production data including deoxidizing degree of refining process,the effect of calcium treatment,the refining treatment time and the secondary oxidation degree in continuous casting process had been investigated to identify the causes of tundish nozzle clogging when producing the aluminized steel. It is found out that Al₂O₃,CaO·6Al₂O₃,CaO·2Al₂O₃ and MgO-Al₂O₃ are the main components in the clog of tundish nozzle. Clogging has caused by irrelevant refining slag system and insufficient calcium treatment. Therefore a modified process had been utilized which led to reduction of the tundish nozzle clogging probability from 8% to below 3%.