Abstract: The flow field and temperature distribution of molten steel in the bloom casting mold have been simulated under the conditions of single straight SEN, side two -furcated SEN, and side quad -furcated SEN by using hydrodynamic software fluent. Results showed that，seeing from flow field,the impingement depth of single straight SEN was the largest, that of side two-furcated SEN was larger, and the depth of side quad-furcated SEN was smallest. The upper and lower double rolls were formed in the side quad-furcated SEN mold. The vorticity of center of the lower roll changed from 590 mm to 270 mm compared with that of single straight SEN ， in favor of the remove of inclusions. As seen from temperature distribution ,the thermal center moved upward obviously and center temperature of the shell increased 6 K and 4 K respectively with the side two -furcated SEN and the side quad-furcated SEN, which contributed to the melt of mold power.