A mononuclear Cu complex Cu_0.5(4,4'?bipy)(H₂O)·L·0.5(4,4'?bipy)·2H₂O (1) was obtained by hydrothermal reaction with Cu²⁺ as the central ion and 4,4'?bipy as the nitrogen?containing auxiliary ligand. Its structure and composition were characterized by modern characterization methods, such as X?ray single crystal diffraction, elemental analysis and infrared spectrum. The results show that Cu²⁺ is six coordinated with four nitrogen atoms of 4,4'?bipy molecules and two oxygen atoms of H₂O molecules, showing a distorted octahedral coordination configuration. L^2- anion only balances the positive charges in compound 1 and does not participate in the coordination of metal Cu²⁺. Cu²⁺ coordinates with 4,4'?bipy and H₂O molecules to form a lattice layered structure [Cu(4,4'?bipy)₂(H₂O)₂]²⁺, the hydroxyl group of L^2- anion and free H₂O molecules form hydrogen bonds with H₂O molecules in the layered structure respectively, which increases the thermal stability of H₂O molecules in compound 1. The fluorescence emission of compound 1 is at 409 nm, which can be attributed to the intraligand emission state. Compared with the ligand, there is a slight red shift, which may be caused by the coordination between 4,4'? bipy ligand and Cu²⁺.