Abstract: Aiming at the uncertain multi-attribute decision making of interval numbers, the density operator was extended from exact values to interval numbers. First, the notion of interval attaching degree was introduced so as to cluster interval numbers, and the density weighting vector was determined by adopting a programming model. Then based on this, the interval number density middle (IDM) aggregation operator and its composite operators were defined. At last, one example was given to illustrate the application of this interval number density operator. By integrating the features of interval numbers, this method can further expand the theoretical system and application fields of density operators.