System architecture is an important work in the process of developing software, but also a core element of the software system, but also the foundation which other parts of building a software system based on, as technology information continues to progress, the scale of the information systems gradually expandes, the complexity of the business becomes much more higher, the system is especially important to the structure in improving the development quality of software system and in terms of modifiability, so that which the system architecture is good or bad will fundamentally decide the quality of software system which is based on this framework and constructed.Software product which is initially developed is carefully designed with good structure, but as time progresses, and as demand varies, the original function must constantly be modified, and the new features will be added, but inevitably there are some shortcomings need to be changed. In this case, the software must make the appropriate changes to maintain their vitality. Sometimes it is inevitable to violate the original design framework.Firstly, the article analyzes and summarizes the results of main theoretical studies which the domestic and foreign researchers obtain, and on the basis of that, the content and objectives of the study.are presented. Then the article is based on the discussion of relevant concepts and definitions, describes the definition and the basic principles of system architecture design; describes the common architecture patterns, design patterns, and describes in detail how to import Factory,Abstract Factory, Strategy, Observer and other design patterns from the perspective of the software changes in demand, and the architecture of the system is designed by binding mode and multi-storey building structure.Secondly, the paper has the navigational business system as an application background, and models the navigational business system through the analysis of needs. It is focused on the optimization of the system architecture design steps on the current problems of navigational business system. The design patterns are gradually and evolutionarily introduced by using object-oriented and interface design, the principles of packaging and the changes of isolation, and the paper will put them together and they will organically be integrated into the navigational business system. And the paper will reference architecture constructed to reconstruct navigational business system, the diagram of optimization of navigational business system architecture is given.Finally, this paper is a concrete realization of the navigational business system in the data access layer, business logic and presentation layer design. The architecture of navigational business system before and after optimization is comprehensively analyzed and compared.Practice proves that the proposed based on NET Framework multi-layer system architecture and integrated application of various design patterns has a very important guiding significance and practical value on the development of the application system.