Abstract: A method to make air combat decision, the quantitative air combat decision, was presented. Based on the launch envelope and the launching condition of air-to-air missile, the air combat situation could be described quantitatively by defining the air combat situation function. Choosing the suitable maneuver according to the values of the air combat situation function and the characteristic of the long-range and the short-range air combat, the relationship between the maneuver strategies of air-combat and the state variables of air-combat situation was built. It was to be made possible to calculate the strategies of air-combat quantitatively from the state variables of air-combat situation, one of which was the effect, the other was the cause of reasoning. The process of analysis, evaluation, decision-making, maneuvering was completed quantitatively. The model of the fighter, target, missile and decision module was built. Giving different initial conditions, the effectiveness of the decision of the long-range air combat and short-range air combat was validated respectively.