People use statistical and simulation methods traditionally to analyze operational effectiveness of the combat system. These methods fail in detailedly describing the impact of human operations in actual combats and the causal relationship among various attributes of elements in the system. From the perspective of methodology, the effectiveness of the combat systems is affected by the combined effects of equipment, man and the environment. Therefore, an analytical method is required. By characterizing the internal relationship and human operations of combat systems, a linear system framework is constructed to analytically evaluate the operational effectiveness of combat systems. In addition, a case study is given to analyze the robustness of the system and to obtain the quantitative impacts of key system attributes through the proposed method. In this case study, the validity and rationality of the method are illustrated and validated.