A tunable metamaterial nanograting coupler (MNC) is presented that is composed of a one-dimensional surface nanograting coupler with a bottom reflector and the metamaterial atop. For a single nanograting coupler, by introducing a reflector and optimizing nanograting parameters, the spatial coupling efficiency exceeds 97% around near-infrared wavelength of 1.43 μm. The metamaterial can be tuned by using micro-electro-mechanical system (MEMS) technique. The relative height or lateral offset between metamaterial and coupling nanograting can be controlled, that the light-emitting efficiency can be separated into two different directions. In addition, the coupling efficiency is as high as 91% at the optical C-band communication window. Therefore, the proposed MEMS-based MNC not only has the possibility of coupling optical fibers with high-density integrated optoelectronic chips, but also has potential application prospects in light path switching, variable optical attenuation, and optical switch.