Evolutionary acquisition is an alternative to the grand design acquisition approaches. It has activities to make it possible to develop quickly and respond flexibly to changing customer needs and technological opportunities. The Ministry of Defense adopted an evolutionary strategy to acquire defense information systems. but it does not work well always. We look at problems from aspects of acquisition system and project management. We benchmark successful cases for evolutionary acquisition strategy in the DoD, the pubic and the private sector. We suggest an evolutionary strategy for defense information systems. The evolutionary strategy in this study includes an evolutionary acquisition framework, an evolutionary acquisition process, and an evolutionary acquisition guideline for defense information systems. The evolutionary strategy can help to implement evolutionary acquisition process for defense information system, and the process can increase the success rate of projects.