In this study, we demonstrated a microfluidic droplet generator system for synthesizing unique 3-D graphene structure. Different concentration and size of graphene oxide (GO) sheets were tuned in the droplets, and the produced droplets were collected on a silicon wafer and evaporated in the tube furnace. By controlling the amount of oil on the silicon wafer during thermal evaporation, the GO sheets were self-assembled in a different way to form unique 3D graphene microstructures including spherical, twisted and hollow hemispherical structure. The size of the 3D graphene structure could be also controlled by the concentration of GO.