Abstract: Reasonableness of structure of the tundish of stainless steel slab casting had been studied by water model experiment.To aim at the influencing factors of flow field in tundish and the existing problems respective,flow control device was optimized through orthogonal optimization tests.The results showed the opening size of lower retaining wall is the key factor of influencing flow field.Considering RTD and flow field display synthetically,while liquid level retained stable,the insertion depth is 180 mm and the casting speed is 1.2 m/min,optimal process parameters is as follows,the distance from upper weir to ladle bottom is 375 mm,the height of upper weir is 208 mm,the distance from upper weir to dam is 575 mm,height of the dam is 100 mm,the opening of the dam is 0 mm.Compared with the prototype tundish,the flow field is improved to a great extent,average retention time is prolonged,the proportion of dead zone decreases,short circuit flow is effectively improved,molten steel becomes uniformity and inclusions clump and grow sufficiently.The results of industrial test showed that under the optimum condition of weir for tundish,purity of casting slab was greatly improved and reject rate of cold rolled sheet reduced.