An approximate dynamic programming approach was developed to generate intelligence maneuvering decisions for CGF (Computer Generated Forces) during one-on-one air combat simulation. Simplified kinematic equations of aircraft were built up in flight-path coordinate system, the 3 DOF (degree of freedom) control command was improved, and the common basic flight maneuvering set was described quantitatively. Then, a new method of air combat maneuvering decision was designed according to actual battlefield situation, using trajectory sampling, feature extraction, policy learning. With this method, CGF can learn an approximately optimal policy of air-combat maneuvering during real-time simulation. Result of simulation confirms that proposed method can improve the intelligent decision ability of CGF during simulated air combat training.