Aiming at the problem of threat assessment of air and space target, a new algorithm for target threat assessment and ranking in intelligent aided decision system is proposed. The algorithm uses the radar characteristics of the targets, such as velocity, acceleration, altitude, heading and electronic interference, as target threat assessment features. Then the Analytic Hierarchy Process (AHP) method of multi-attribute decision is used to fuse information, and the judgment matrix of attribute importance is constructed by fuzzy dynamic interval method, which effectively solves the problem of attribute weight changing with time. Finally, the threat degree is determined by sorting the fusion results. The simulation results show that the algorithm is effective.