In order to evaluate the weapon system effectiveness, American Weapon System Effectiveness Industry Advisory Committee advanced the ADC model. The model enhances the system integrity of weapons' structure, technical feature and tactical function. The defect of the traditional ADC model lies in the complex calculation procedure. Also, the evaluation is only confined to the basic effectiveness. The effectiveness of weapon system based on the conflict circumstance in reality can't be evaluated. This paper, based on the traditional ADC model, puts forward a simplified algorithm by referencing the thought of Markov process and establishes an improved ADC model by which the conflict circumstance is overall considered in reality to make the qualitative problem quantized. A real case is analyzed to confirm the effectiveness and scientificness of the new model. The paper shows particular concerns about the target missiles defense penetration ability, which is of some reference value to the weapons' conceptualization, initiation and design.