Abstract: If a classic combined approach is used to analyze the residue time distribution (RTD) curve in a tundish, the volume ratio of the dead zone in the multi-strand tundish sometimes is negative. In addressing this problem, a comprehensive analytical approach was used to pre-treat the RTD curve of each strand in the multi-strand tundish to get the characteristic RTD curve, and then a classic combined approach was used to treat the characteristic RTD curve, with the whole characteristic parameters obtained to determine fluid flow in the multi-strand tundish. The water model result for the RTD curve of an asymmetrical two-strand tundish showed that the negative volume ratio of the dead zone appeared with Sahai's revised approach. Mean residence time is the key parameter to estimate the similarity of flow characteristics of each strand in the multi-strand tundish. The minimum mean residence time for each strand is the key parameter to investigate the fluid flow in the multi-strand tundish.