Abstract: A ranking method of the intuitionistic fuzzy set (IFS) which fuses the information of targets in multiple times is proposed to solve the threat assessment problem in the air defense operation. First, subjective attribute weights and objective attribute weights are integrated to structure the comprehensive attribute weights. Then, the technique for order preference by similarity to ideal solution (TOPSIS) is utilized to characterize the amount of information of IFSs, and the intuitionistic fuzzy entropy is calculated to measure the reliability of information. The amount and the reliability of information are integrated considering the decision makers’ risk attitude and a ranking measure for IFSs is developed and used for the threat ranking of targets in single time. Finally, the decision information in multiple times is fused by the structured time sequence weights, whose form is Poisson reverse distribution, to rank final threat levels of targets. The simulation results show that the proposed method possesses properties of reliability and efficiency by synthesizing the decision information in multiple times and being able to be adjusted according to the decision makers’ risk attitude.