Abstract: By using the commercial code CFX, the three-dimensional model to simulate the fluid flow in slab continuous caster mold has been set up. This mathematical model is proved by the experimental results of water model. By using this model, the effects of the SEN outflow angle, immersion depth and casting speed on velocity fields in the slab mould are studied. This model is an efficient means for optimizing the structure of the mould and the submerged entry nozzle (SEN).