Alumina inclusions generated during deoxidation and reoxidation processes of the steel were easy to accumulate on the inner side wall and outlets of the submerged entry nozzle (SEN), which led to nozzle clogging during continuous casting process. Thus, the clogging material on SEN walls was investigated. Measures to prevent nozzle clogging during continuous casting were summarized, including lowering the number of inclusions in steel, improving the preheating of the SEN before casting, preventing the reoxidation of the molten steel during casting, and optimization of nozzle materials. Flow patterns in the mold during slab continuous casting had a direct influence on the slag entrainment in the mold. Nail board experiments were performed to obtain the correct relationship between argon blowing flow rate at the SEN and steel throughput to assure a double roll flow pattern in the mold which lowered slag entrainment.