This paper describes Object-oriented Modeling and Simulation of RISA(Real-time distributed System for Air defense), especially focused on advanced software engineering method using design patterns including object-oriented modeling method by UML (Unified Modeling Language). Modeling by UML presented by several diagrams helps users develop the relevant domain-specific models and provides the foundation to build robust software architecture based on HLA (High Level Architecture). The RISA system composed of six components (federates) - SMCC, MFR, ECS, LAU, ATS, MSL - is constructed by object-oriented design patterns related to HLA-based techniques. Design patterns in RISA are divided into four categories. The first design pattern category related to user interface (UI) includes Active Object pattern, Model-View-Controller (MVC) pattern. The second related to Domain-specific layer contains facade pattern for unified interface of database and integrator pattern for many models. The third related to database has Persistence Layer pattern for persistent objects. The fourth related to synchronization includes Strategy pattern for time synchronization including time-stepped, event-driven and optimistic mechanisms and Command pattern for callback. The object-oriented design through modeling in RISA provides the system with modification, extensibility, flexibility through abstraction, encapsulation, inheritance and polymorphism. Also, design patterns which are reusable solutions to recurring problems that occur during software development simplify the software development process and reduce costs because the reusability of software is increased when a system is developed.