Abstract: The surface fluctuation and slag entrapment involved in the wide slab continuous casting mold of 150 mmí1503 mm in a steel plant was caculated by FLUENT software. Surface velocity was set as the main measure to study about port angle and guide an-gular shape of the nozzle influence on flow field. The calculation results show that under the condition of original nozzle, the surface velocity was large, but the impact depth was small and the fluctuation was severe. Entrapment of slag was serious. After changed the angle of the outlet, the mold surface velocity remained large and severe entrapment of slag. When scheme 3 (outlet lead angle changed shape to tangent) was applied, surface velocity reduced from 0.6 m/s to 0.2 m/s, impact depth improved, flow field character became better, and problem of slag entrapment was resolved.