Recently, gradient meta-surface has become an important and hot sub-branch in electromagnetic metamaterial research. In this paper, we review some recent progresses in this area, such as using gradient meta-surfaces as a bridge to link propagating waves and surface waves and the conversion efficiency issue related to such conversion, high efficiency broadband anomalous reflection by optical gradient meta-surfaces, the development of a mode-expansion theory for studying the scattering properties of inhomogeneous meta-surfaces, flat meta-surfaces to focus electromagnetic waves in reflection geometry and the comparison of reflective and transmissive gradient meta-surfaces. Finally, we present our perspectives on the future direction of this research field.