This article introduces characteristics and development of BIM system and cloud computing and demonstrates some views about the application mode of the BIM system in the cloud computing background. The features of the cloud computing can meet the requirements of the development of the BIM system, and the BIM ware (the BIM software system) based on cloud computing technology will better integrate data and functions. The new computation mode and the BIM system will benefit the users and the whole CAD market and meet the low carbon trend.