Abstract: In recent years, the number of extreme weather events rose greatly, especially larger flood disasters, happening more frequently and impacting more seriously. Based on numerous concepts of vulnerability, urban vulnerability was clarified, and an evaluation index system of urban flood disaster vulnerability was constructed. As one of methods of multiple attribute decision making, Technique for order preference by similarity to ideal solution (TOPSIS) could not compare the dots on the mid-perpendicular of positive ideal solution and negative ideal solution. Kullback-Leibler distance was used to calculate the similarity degree between the evaluation object and positive ideal solution. And then, this KL-TOPSIS model was made use to evaluate the Harbin's flood disaster vulnerability from 2005 to 2009 dynamically with the conclusion that it first increased and then dropped. Through the horizontal comparison, it was found that Harbin's flood disaster vulnerability was less than contemporary Shenyang, Wuhan and Shanghai.