In studying the dynamic and steady behavior of distillation columns, identifying the liquid flow pattern is very important. The type of liquid flow pattern on each tray depends on design parameters such as column diameter and tray spacing and operating variables such as liquid and vapor flow rates. The innovative technique presented in this paper can help us to recognize the tray flow pattern type with MADM method. A case study is presented to illustrate the method. (c) 2006 Elsevier Ltd. All rights reserved.