To adapt to the changes in generation mode and evaluation means of combat effectiveness of information-based and intelligent air & space defense systems， this paper analyzed the operational mechanism of air & space defense kill chain based on order by a combination of military theory and technical practice. On this basis， evaluation methods for the combat effectiveness of two kill chains based on positive and negative feedback mechanisms of system theory and complex network analysis of the combat cloud were studied. This aims to quantify the combat effectiveness of order-based kill chains in future air & space defense operations and describe the complex correlation and dynamic coupling mechanism among operational elements in different operational areas within the system in air & space defense operations， thereby providing data support and theoretical reference for improving the overall combat effectiveness of air & space defense systems. The feasibility and effectiveness of two evaluation methods for combat effectiveness were verified by taking a typical air & space defense kill chain as an example.