Communication and information technologies are used by intelligent transportation systems (ITS) to manage traffic flow data and enable people to obtain the services for safe and comfortable driving. Cloud computing can help to handle the large amount of storage resources and mass traffic flow data effectively and efficiently. Intelligent traffic cloud could provide services such as autonomy, mobility, decision support and traffic management strategies, and so on. This paper analyzes the architecture of the ITS using cloud computing and proposes a new architecture that tries to improve the current architecture and reduce the limitation by using cloud computing technology. The architecture organizes, manages and goes to access traffic knowledge from data that are achieved from sensors, vehicles, roadside infrastructure and etc, by using data mining technology. The services and applications of the system are provided through the cloud computing technology.