Abstract: The 3D mathematical model of fluid flow,heat transfer and species transportation has been used to optimize the flow control device of a T shape eight-strand billet continuous casting tundish.The flow field,temperature filed,residence time distribution of the molten steel have been computed and analyzed for different flow control cases.The results indicate that short-circuit flow and large dead zone exist without use of flow control devices,and both temperature and residence time are much different between closer and farther outlets,which implies unproportional flow field.The existing flow control case eliminates the short-circuit flow and reduces the dead zone,but the flow proportionality shows no observed improvement.Further improvement has been achieved when the optimized case is used.The residence time of different outlets is uniform on the whole and the temperature difference between the outlets is diminished,which shows the flow proportionality is significantly improved.