Weapon systems are curcial instruments for the security of a nation and critical elements for the victory in a war. Since modern weapon systems tend to be capital-intensive with high precision and quality, they become more and more complex and diversified; their acquisition costs become huge; and their technological obsolescence becomes accelerated. Therefore, the systematic management of weapon acquisition process would be one of the most important defense tasks at the national level. To analyze such problems and find solutions, this paper has studied various aspects related to the efficient management of weapon system acquisition. After brief summarization of the general characteristics of weapon systems, their effectiveness, and developmental trend, the paper discusses the defense management policies and techniques for the weapon systems. Specifically, four alternative acquisition methods such as indigenous R & D, foreign purchase, co-production and joint-production are discussed and analyzed by systems approach. The systems analysis procedure to evaluate and select weapon acquisition method is as follows; 1) to analyze the merits and demerits of the alternative methods, 2) to screen unrealistic alternatives through the consideration of significant factors such as political, economic, military, technological, and social constraints, 3) to evaluate and select an optimal one among the remaining acquisition methods after the cost-effectivenss analysis. For the base of cost-effectivess analysis, cost analysis model as well as effectiveness analysis model of each acquisition method are developed.