Taking joint air operations as the background, an air cluster threat assessment method based on the change of battlefield situation is proposed. First, a threat assessment index system for air cluster is established, and a quantified threat index model based on hierarchical aggregation is constructed based on the similar principles of discrete sources and weapons and equipment; the subjective and objective weights are obtained by the analytic hierarchy process and the entropy weight method, and the constant weight is obtained by the game combination. the variable weight theory is introduced to determine the variable weight, so that the index weight can reflect the characteristics and changes of the battlefield situation; then, the traditional multiattribute decisionmaking method does not consider the psychological factors of the decision maker and the gray correlation analysis and the TOPSIS method evaluation results are inconsistent. A grey TOPSIS threat assessment model based on regret theory is proposed, and the final threat assessment result is obtained by calculating the comprehensive closeness. Finally, the effectiveness of the method is proved by simulation experiments.