Abstract: Micro-nano optical fiber sensor combines with micro-nano processing and optical fiber sensing technology, which has great significance in scientific research and industrilization potential. The preparation of the arbitrary complex three-dimensional (3D) structures cannot be achieved by the existing processing methods, thereby limiting the development of the micro-nano optical fiber sensor. A new processing method of micro-nano was proposed, which could achieve the preparation of the micro-nano structure on the polydimethylsiloxane (PDMS) thin films, then transferred the thin films and the micro-nano structure to the end face of the optical fiber, and the 3D micro-nano structure with artificial definition was achieved. The prepared samples are examined under the scanning electron microscope, and it is confirmed that the PDMS thin film and its 3D structure can be transferred to the end face of the optical fiber without loss. The proposed method has the characteristics of easy preparation, low cost and processing 3D micro-nano structure.