In the modern warfield, as the defense systems has been digitalized, intelligent, and working with network, the importance of interoperability among the systems has been also increasing. KMND(Korean Ministry of National Defense) has developed and used the SITES(Systems Interoperability Test & Evaluation System) based on Korean LISI(Levels of Information Systems Interoperability). SITES had been developed in order to evaluate the interoperability among information systems from the viewpoint of technical attributes. In this paper, we propose the extended interoperability evaluation model which can be applied not only the information systems, but also the weapon systems. Moreover, the extended interoperability evaluation model also includes the consideration of non-technical attributes.