Single molecule magnets are potentially useful in quantum computing, high density data storage and molecular spintronics. 3d transition-metal-based single-ion magnets have attracted intensive interest because their structures are simple, and it is easy to explore the magneto-structural relationship, and achieve the higher barriers by tunable ligand field. Unifying the domestic and foreign research situation, the paper will show an overall perspective of the present single-ion magnets(SIMs) based on the 3d transition metal with the coordinated geometry, and highlight the relationship among the ligand field, the magnetic anisotropy and the behavior of single molecule magnet, which will provide a new route for the syntheses of single molecule magnets.