The invention provides a method for realizing a three-dimensional virtual city system based on the RIA (rich Internet application) architecture, which is a method of truly representing urban geographic space and environment on the Internet network through virtual three-dimensional visualization. The method comprises: at first, generating a three-dimensional virtual city scene through space data collection, three-dimensional model building, partition rendering and seamless splicing based on the RIA architecture, then creating a three-dimensional tile data set through a computer caching technology, combining a Web server technology and a GIS (geographic information system) server technology on the basis of the three-dimensional tile data set, and developing the three-dimensional virtual city system with map bookmarks, tour queries, map markers, map correction and map advertising functions under supporting of an RIA client platform. The drawing, display and dissemination of the conventional two-dimensional map are changed, reference can be provided for daily life, travel and online affairs of people living in cities, and an interactive channel is provided for propaganda of urban governments, institutions, businesses and enterprises to the public.