Abstract: In the era of new urbanization, industrialization and informatization, China's cities confront much complex problems on the way to further city with sustainable economy, society and ecology. Now, city applications integrating Geomatics, Internet and cloud computing generates urban big data, which become strategic resources of smart city. With the cross-fusion of Geomatics, Informatics and urban science, Urban Informatics, a new direction of surveying, mapping and geoinformation, is developing. Based on the unified spatial-temporal datum, urban informatics is to capture, process, analyze urban big data, and make smart decision with the help of information technology, aiming to realize the green, low carbon, and sustainable city. This paper discusses the relationship between Geomatics and urban informatics, and five characteristics of urban informatics, including dynamic evolution, data-driven, crowdsourcing learning, collaborating decision, and cross-disciplines. Finally, it summarizes scientific questions and outlook the further of urban informatics.