The tactical situation assessment is the basis of Mission Planning, Emergency Action Planning, Firepower Assignment and Attack Ordering in PAAIS (Pilot Assistant Artificial Intelligent System). To take into account the current BVR (Beyond-Visual-Range) air combat threat assessment, we proposed a method which used the TOPSIS (Technique for Order Preference by Similarity to Ideal Solution) arithmetic to evaluate the air target threat. Compared to the other threat methods, this arithmetic has the characteristic of simple, computation fast, update expediently and so on. The simulation result indicated that it can respond quickly to the detected targets and satisfy the requirement of situation assessment in PAAIS.
