Abstract: In the past years, the prosperous progress of additive manufacturing , promotes a rapid development of the mechanical architected metamaterials. In this paper, the design and the excellent mechanical properties of these metamaterials are introduced, including the following parts: the evolutional development of the unit cell design from beam-based, plated-based to shell-based structures in order to reduce the intrinsic stress concentration; the route to achieve the isotropic Hashin-Shtrikman stiffness limit; their applications in various fields of biological medicine, energy, environment, and others.