Abstract: The clogs on the submerged entry nozzle of type 304 and 321 stainless steels were investigated, and the mechanisms of clogging were discussed. The results indicated that deposits on the nozzle in type 304 stainless steel consists of Al₂O₃, MgO·Al₂O₃ and some metal. Because of the thin deposits, the casting was not affected obviously and could be improved by controlling Al < 0.01 %. There are two kinds of clogging, namely TiN-type and CaO·TiO₂-type clogging, in the casting of type 321 stainless steel. TiN-type clogging consists of a lot of TiN inclusions and some metal, and could be improved by Ti%·N%×10³ < 3.5 and Al < 0.01% in liquid. CaO·TiO₂ type clogging consists of CaO-TiO₂-MgO-Al₂O₃ and a lot of metal, and could be improved obviously by reducing the amount of CaO-TiO₂-MgO-Al₂O₃ inclusions in molten steel.