Optical chiral metasurfaces are 2D or quasi-2D photonic devices composed of subwavelength-scale units, which combine novel physics and cutting-edge nanofabrication development, can generate extremely strong optical chirality, and have broad application prospects, including chiral sensing, chiral particles separation, and active control. This paper introduces the fundamental mechanisms of chiral metasurfaces, summarizes domestic and foreign state-of-the-art studies from the perspectives of metallic and dielectric materials, and focuses on the circular dichroism and near-field chiral responses. This paper also addresses the application areas of chiral metasurfaces.