Abstract: The study was based on the 1∶2 water model of tundish. The flow field in tundish before and after the installation of tunnel type filter were studied through physical simulation. The influence of flow field with different exit angle of filter and the height of the retaining dam were analyzed. The results show that the tunnel type filter in tundish can not only filter the molten steel, but also optimize the flow field in tundish with other flow modifiers.All these give a new choice on how to reduce inclusions. The plan set the exit angle of filter is 20°, and the height of the retaining dam is 350 mm. It can optimize the flow field in tundish, reduce the dead zone volume fraction effectively, increase the volume fraction of plug-like and prolong the average residence time of molten steel. It makes the conditions of inclusion floatation removal better.