A fabrication method of nanoparticles is provided. A substrate having a plurality of pillar structures is provided and then a plurality of ring structures is formed to surround the plurality of the pillar structures. The inner wall of each ring structure surrounds the sidewall of each pillar structure. A portion of each pillar structure is removed to reduce the height of each pillar structure and to expose the inner wall of each ring structure. The ring structures are separated from the pillar structures to form a plurality of nanoparticles. Surface modifications are applied to the ring structures before the ring structures are separated from the pillar structures on the substrate.