Taking the actual combat system as the research object, this work studies the modeling and evaluation methods of combat systems theoretically based on the complex network theory and modern combat cycle theory. Firstly, an investigation, decision, fire, communication, and support (IDFCS) combat model based on functional combat model is proposed, with its modeling method and generation algorithm introduced, which can quantitatively describe system armament capability and combat system rules from a more realistic and detailed perspective. Secondly, this work introduces a system effectiveness evaluation method and armament importance evaluation method based on IDFCS model and operation loop theory, which can quantitatively analyze the effectiveness of combat system by using the capability attributes of armaments. Finally, the work generates the combat system sample networks of different scales with the model's generation algorithm and evaluates its effectiveness, which provides theoretical support for further research of system operations.