Abstract: Water modeling and numerical simulation were applied to investigate the influence of the port angle of a submerged entry nozzle (SEN) on the flow pattern in a slab continuous casting mold. The results indicate that under the current 15° SEN, the surface velocity and fluctuation are relatively small at meniscus, which does harm to the melt of mold powder. The impinging point of jet flow streaming from the SEN is relatively low. Below the point, the pressure on the solidifying shell is relatively high. The sharply decreasing frequency of breakout alarms and no breakout were achieved after a new 10° SEN was put into operation.