Existing mobile networks suffer from complex protocols, inflexible equipment, and vendor specific configuration interfaces and other problems. This paper proposes a novel framework, NO Stack (short for “Not Only Stack”), which is a software-defined framework for 5G mobile network. NO Stack emphasizes on the decoupling of the user plane, control plane and management plane, pushes down the layer-by-layer protocol stack. In this paper, three key technologies are introduced: flat user plane, global network view (GNV) and on-demand network slice. The demo instance is set up to certify NO Stack can implement the virtualization shield of the infrastructure resources, to enable the highly elasticity of the network and seamless migration.