This paper proposes a Cloud Evolved Packet Core (CEPC) architecture based on Software-Defined Networking (SDN)/OpenFlow technology, which separates the control plane and data plane of a Serving GateWay (SGW) and a PDN gateway (PGW) completely, and runs the control functions of a Mobility Management Entity (MME), SGW-C and PGW-C of the LTE-Evolved Packet Core (LTE/EPC) architecture in the cloud controller. By simulating the initial attach process of the CEPC architecture and the traditional LTE/EPC architecture, it is concluded that the CEPC architecture has a lower paging signalling load, and the network flexibility and programmability are higher.