The objective of this paper is twofold. One is to review the warranty concept and present situation in the defense equipment acquisition. This paperdescribes the types of warranty policies(Free-Replacement Warranty(FRW), Pro Rata Replacement Warranty(PRW), and Combined FRW/PRW) and the cost models to deal with warranty economic decisions(Nonrenewing Warranty, Renewing Warranty). The other objective is to apply the economic model to establish the warranty period in the small numerical example. This study shows that (1) low reliability items rapidly raise the total expected cost when the warranty time is extended; (2) if the item's reliability is increased, the nonrenewing free-replacement warranty policy is the most effective one to reduce the total expected warranty cost.