A cloud computing architecture with four levels was presented.The notion of resource as a service RAAS was proposed and interpreted.Compared with existing cloud computing architectures,it reflects the core characteristics of cloud computing technology more exactly.The definitions of cloud and cloud computing were given from the standing point of data resource.The data acquisition model was designed.The way of selecting the processing equipment in cloud environment in term of data resource was described,which provides a new direction for the application of cloud computing.