The influence of trumpet-shaped ladle shroud and straight ladle shroud on characteristics of fluid flow in a single strand slab tundish under different liquid levels through physical simulation is studied. The results show that the peak value of RTD curves after using trumpet-shaped ladle shroud is relatively low， the curves become smooth， the flow field is relatively stable and there isn’t short circuit flow. Also, the respond residence time, the mean residence time and the plug residence time of the liquid in tundish are prolonged. Besides, when the trumpet-shaped ladle shroud is used, the dead volume fraction is smaller， the plug volume fraction becomes larger and the ratio of the plug volume fraction to the dead volume fraction is greater. Therefore, when the liquid level of tundish is going up, its flow pattern becomes more reasonable after using trumpet-shaped ladle shroud, which is in favor of improving the quality of molten steel in tundish.