This article presents a flexible architecture of a Web-based tool that serves as a platform for power system visualization with open data structures. Different from regular applications, this platform may be viewed as a semicompleted application. It implements common features of a power system application such as GIS-like drawing and visualization, built-in topology processor, and so on. Meanwhile, the platform defines open data structures for system components with the consideration of efficiency and flexibility. It also provides a mechanism to link itself with external engines, instead of implementing the engines directly. This architecture may achieve considerable flexibility. For instance, users may extend and customize data structures of power system components. Users may also develop their own analytic engines based on their specific needs and link them with the platform. To maximize the benefits to users, the proposed platform is Web-enabled with Java client-side technology. It is universally accessible, instantaneously upgradable, and operating-system independent.