To solve the limitations of the test scope, test period, and budget, we have been adapting Modeling and Simulation (M&S) techniques for Test and Evaluation (T&E) of the state-of-the-art weapon systems. This paper describes the Real-time Distributed Simulation Environment (RDSE) for the Korea’s medium-range surface-to-air missile system (Chelmae-II). The RDSE will be used to support the test bed and performance analysis tools for the Chelmae-II system. To develop the RDSE, this paper proposes the Air Defense Simulation Framework (ADSF) which supports the High Level Architecture (HLA) and the TCP/IP as well as a real-time simulation engine. An ADSF was successfully applied to the RDSE, and a satisfied test result was acquired through the Global Positioning System (GPS) timer.