Abstract: The research is aimed at key characteristics of City Information Model (CIM) on level and classification. CIM could provide multi-scale 3D data base and scientific decision support for city planning, construction, management and operation, which becomes a part of 14th five - year national economic and social development planning in China. CIM has the complex characteristics of multi-scale, multi-specialty and multi-industry cross-integration, which is difficult to guide the integrated application and sharing information of models. The establishment of a unified levels and classification of CIM will effectively improve the situation. By comparing and analyzing the existing standard systems of City three-dimensional model, CityGML classification and Building information model (BIM), comprehensive concept and levels of CIM are deeply explored. This paper proposed a gradually refined levels of CIM from 1st to 7th, which includes terrain surface model, frame model, standard model, fine model, functional level model, component-level model, and part-level model. The content, feature and precision of seven-level models were described and preliminarily verified. Based on BIM classification, this paper used faceted classification method to define and expand CIM classification., including the five dimensions of result, process, resource, character and application. This research explored the levels and classification characteristics of CIM, which contribute to the creation, procedure, display, sharing and application of CIM. 

Key words:  , city information model, levels of CIM, classification of CIM, building information model, geographic information system