Abstract: With scaling down of the size of electrical devices, molecular electronics, which uses single molecules as circuit components, has become vitally important．In molecular electronics, single-molecule devices not only provide potential solution for miniaturization of future circuit devices, but also contain novel physical properties due to the unique nanometer scale．Construction methods of single-molecule devices are reviewed, as well as their novel electrical, magnetic and quantum properties, and corresponding regulation methods．Developments of monomer devices are summarized, potential breakthroughs in molecular electronics are proposed．